:root {
    --primary-color: #007bff;
    --primary-hover-color: #0056b3;
    --secondary-color: #6c757d;
    --secondary-hover-color: #5a6268;
    --success-color: #28a745;
    --success-hover-color: #218838;
    --danger-color: #dc3545;
    --warning-color: #f39c12;
    --warning-hover-color: #e67e22;
    --light-bg: #f8f9fa;
    --light-border: #dee2e6;
    --text-color: #333;
    --white-color: #fff;
    --body-bg: #f4f4f4;
}

body,
html {
    max-width: 100%;
}

body {
    font-family: apple-system, BlinkMacSystemFont, sans-serif;
    margin: 0;
    background-color: var(--body-bg);
    color: var(--text-color);
    font-size: clamp(16px, 1rem + .2vw, 18px);
    line-height: 1.6;
}

.page-content-wrapper {
    width: 100%;
    overflow-x: hidden;
}

.main-title-container,
.quiz-container,
footer,
nav {
    box-sizing: border-box;
}

.nav-container {
    position: sticky;
    top: 0;
    z-index: 100;
    width: 100%;
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1100px;
    margin: 0 auto;
    background-color: var(--white-color);
    box-shadow: 0 2px 8px rgba(0, 0, 0, .1);
    padding: 0 15px;
    border: solid 1px #ccc;
}

.menu-list {
    display: flex;
    justify-content: flex-start;
    align-items: center;
    list-style: none;
    margin: 0;
    padding: 0;
    flex-grow: 1;
    margin-left: -15px;
}

.menu-item a {
    display: block;
    padding: 18px 20px;
    color: var(--text-color);
    text-decoration: none;
    font-weight: 600;
    font-size: 1em;
    transition: all .3s ease;
    border-bottom: 3px solid transparent;
}

.menu-item a:hover {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
}

.menu-item.highlight-item a {
    background-color: var(--primary-color);
    color: var(--white-color);
    border-radius: 5px;
    border-bottom-color: transparent;
}

.menu-item.highlight-item a:hover {
    background-color: var(--primary-hover-color);
    color: var(--white-color);
}

.hamburger-menu,
.mobile-header {
    display: none;
}

.main-title-container {
    max-width: 1100px;
    margin: 20px auto 0 auto;
    padding: 20px 15px;
    background-color: var(--primary-color);
    border-radius: 8px;
    box-shadow: 0 2px 8px rgba(0, 0, 0, .1);
    text-align: center;
}

h1,
h2 {
    color: var(--primary-hover-color);
    margin-bottom: 20px;
    text-align: center;
}

.main-title-container h1 {
    margin: 0;
    color: var(--white-color);
    font-size: 1.6em;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.quiz-container {
    background-color: transparent;
    box-shadow: none;
    padding: 0;
    max-width: 1100px;
    margin: 20px auto 30px auto;
    position: relative;
}

.timer {
    position: absolute;
    top: 25px;
    right: 25px;
    font-size: 1.3em;
    font-weight: 700;
    color: #d9534f;
}

#question-text {
    font-size: 1.2em;
    margin-bottom: 20px;
    font-weight: 700;
}

#question-image {
    max-width: 100%;
    height: auto;
    margin: 15px auto;
    display: block;
    cursor: zoom-in;
}

.throttling-question-warning {
    color: var(--danger-color);
    font-weight: 700;
    margin-top: -10px;
    margin-bottom: 15px;
    text-align: center;
    font-size: .9em;
}

.options-list {
    list-style: none;
    padding: 0;
    margin-bottom: 20px;
}

.option-item {
    margin-bottom: 10px;
}

.option-item label {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 15px;
    width: 100%;
    box-sizing: border-box;
    background-color: #e9e9e9;
    border: 1px solid #e9e9e9;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color .2s, border-color .2s;
    -webkit-tap-highlight-color: rgba(0, 0, 0, 0.1);
}

.option-item label:hover {
    background-color: #dcdcdc;
    border-color: #b0b0b0;
}

.option-item input[type=radio] {
    position: absolute;
    opacity: 0;
    width: 0;
    height: 0;
}

.custom-radio {
    display: inline-flex;
    justify-content: center;
    align-items: center;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    border: 2px solid #a0a0a0;
    background-color: var(--white-color);
    flex-shrink: 0;
    transition: all .2s ease-in-out;
}

.custom-radio::after {
    content: '';
    display: block;
    width: 10px;
    height: 10px;
    border-radius: 50%;
    background-color: var(--primary-color);
    opacity: 0;
    transition: opacity .2s ease-in-out;
}

.option-item input[type=radio]:checked+.custom-radio {
    border-color: var(--primary-color);
}

.option-item input[type=radio]:checked+.custom-radio::after {
    opacity: 1;
}

.option-item label span:last-of-type {
    flex-grow: 1;
    line-height: 1.4;
    word-break: break-word;
    min-width: 0;
}

.button-group {
    display: flex;
    gap: 10px;
    margin-top: 20px;
}

.button-group button {
    flex: 1;
    padding: 12px 20px;
    background-color: var(--primary-color);
    color: #fff;
    border: none;
    border-radius: 8px;
    font-size: 1.1em;
    font-weight: 500;
    cursor: pointer;
    transition: background-color .3s ease;
}

.button-group button:hover {
    background-color: var(--primary-hover-color);
}

.button-group button:disabled {
    background-color: #ccc;
    cursor: not-allowed;
}

#review-button {
    background-color: var(--secondary-color);
}

#review-button:hover {
    background-color: var(--secondary-hover-color);
}

#result-summary.correct p {
    color: var(--success-color);
    text-align: center;
    font-size: .9em;
    font-weight: 700;
    margin-bottom: 20px;
    border: solid 1px;
    background-color: var(--light-bg);
    padding: 20px;
    margin-bottom: 15px;
    border-radius: 8px;
    border: 1px solid var(--light-border);
    border-left: 5px solid var(--secondary-color);
}

#result-summary.incorrect p {
    color: var(--danger-color);
    text-align: center;
    font-size: .9em;
    font-weight: 700;
    margin-bottom: 20px;
    border: solid 1px;
    background-color: var(--light-bg);
    padding: 20px;
    margin-bottom: 15px;
    border-radius: 8px;
    border: 1px solid var(--light-border);
    border-left: 5px solid var(--secondary-color);
}

.restart-button {
    background-color: var(--success-color) !important;
}

.choose-other-exam-button {
    background-color: #17a2b8 !important;
}

.print-results-button {
    background-color: var(--primary-color) !important;
}

.certificate-button {
    background-color: var(--warning-color) !important;
}

.selection-screen {
    text-align: center;
}

.guidelines {
    background-color: var(--white-color);
    border: 1px solid var(--light-border);
    border-radius: 8px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, .1);
    padding: 20px;
    text-align: justify;
    margin-bottom: 20px;
}

.guidelines img {
    max-width: 100%;
    height: auto;
    display: block;
    margin: 15px auto;
    border-radius: 5px;
}

.guidelines p,
.guidelines ul li {
    line-height: 1.7;
}

.guidelines-flex {
    display: flex;
    align-items: center;
    gap: 25px;
}

.guidelines-image {
    flex-shrink: 0;
    width: 40%;
}

.guidelines-text {
    flex-grow: 1;
}

.exam-sets-grid {
  display: flex; /* Chuyển sang dùng Flexbox */
  flex-wrap: wrap; /* Cho phép các nút tự xuống dòng */
  gap: 15px;
  margin-top: 20px;
}

.question-nav-menu {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 8px;
    margin-bottom: 25px;
    padding: 10px;
    background-color: #f0f2f5;
    border-radius: 8px;
}

.paging-tabs {
    display: flex;
    justify-content: center;
    gap: 8px;
    margin: 25px 0 15px 0;
    flex-wrap: wrap;
}

.paging-tab {
    padding: 8px 16px;
    border: 1px solid #ccc;
    background-color: #f0f0f0;
    color: var(--text-color);
    border-radius: 20px;
    cursor: pointer;
    font-size: .9em;
    font-weight: 500;
    transition: all .2s ease;
}

.paging-tab:hover {
    background-color: #e0e0e0;
    border-color: #a0a0a0;
}

.paging-tab.active {
    background-color: var(--primary-color);
    color: #fff;
    border-color: var(--primary-color);
}

.question-nav-item {
    display: flex;
    justify-content: center;
    align-items: center;
    width: 35px;
    height: 35px;
    border: 1px solid #ccc;
    border-radius: 50%;
    background-color: var(--white-color);
    font-weight: 500;
    cursor: pointer;
    transition: all .2s;
}

.question-nav-item.current {
    background-color: var(--primary-color);
    color: #fff;
    border-color: var(--primary-color);
    transform: scale(1.1);
}

.question-nav-item.answered {
    background-color: #d4edda;
    border-color: var(--success-color);
}

.question-nav-item.throttling {
    border-color: #c82333;
    color: #c82333;
    background-color: #fffacd;
}

.question-nav-item.throttling.current {
    background-color: var(--danger-color);
    color: #fff;
    border-color: #c82333;
}

.answer-review-section h3 {
    color: var(--primary-hover-color);
    text-align: center;
    margin-bottom: 25px;
    font-size: 1.5em;
}

.question-review-item {
    background-color: var(--light-bg);
    padding: 20px;
    margin-bottom: 15px;
    border-radius: 8px;
    border: 1px solid var(--light-border);
    border-left: 5px solid var(--secondary-color);
}

.question-review-item p {
    margin: 0 0 10px 0;
    font-size: 1.1em;
    line-height: 1.6;
}

.question-review-item .question-text-review {
    font-weight: 700;
    color: #343a40;
}

.question-review-item .your-answer.wrong {
    color: var(--danger-color);
    background-color: #f8d7da;
    padding: 2px 6px;
    border-radius: 4px;
}

.question-review-item .correct-answer {
    color: var(--success-color);
    font-weight: 700;
}

.question-review-item.throttling-question {
    border-left-color: var(--danger-color);
    background-color: #fff3cd;
}

.explanation-text {
    margin-top: 15px;
    padding-top: 10px;
    border-top: 1px dashed #ccc;
    font-size: 1em;
    color: #666;
    font-style: italic;
}

.question-review-item img {
    max-width: 100%;
    height: auto;
    display: block;
    margin: 15px auto 10px auto;
    border-radius: 5px;
}

#review-mode-overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, .7);
    z-index: 1000;
    justify-content: center;
    align-items: center;
}

.review-mode-content {
    background-color: var(--white-color);
    padding: 30px;
    border-radius: 10px;
    box-shadow: 0 5px 15px rgba(0, 0, 0, .3);
    width: 90%;
    max-width: 800px;
    max-height: 90vh;
    overflow-y: auto;
    position: relative;
}

.review-mode-content h3 {
    text-align: center;
    color: var(--primary-hover-color);
    margin-top: 0;
    margin-bottom: 25px;
}

.review-question-grid {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 10px;
    margin-bottom: 25px;
}

.review-question-item {
    padding: 10px;
    border: 1px solid #ccc;
    border-radius: 5px;
    text-align: center;
    cursor: pointer;
    transition: background-color .2s, border-color .2s;
    font-weight: 700;
}

.review-question-item.answered {
    background-color: #d4edda;
    border-color: var(--success-color);
}

.review-question-item.unanswered {
    background-color: #f8d7da;
    border-color: var(--danger-color);
}

.review-question-item.current {
    background-color: #cce5ff;
    border: 2px solid var(--primary-color);
}

.review-question-item:hover {
    background-color: #e0e0e0;
}

.close-review-button {
    position: absolute;
    top: 10px;
    right: 15px;
    background: 0 0;
    border: none;
    font-size: 1.8em;
    cursor: pointer;
    color: #666;
}

.close-review-button:hover {
    color: #333;
}

footer {
    max-width: 1100px;
    margin: 40px auto;
    padding: 25px;
    border: 1px solid var(--light-border);
    border-radius: 8px;
    background-color: var(--white-color);
    text-align: center;
}

footer p {
    margin: 10px 0;
    font-size: .9em;
    color: var(--secondary-color);
    line-height: 1.6;
}

footer a {
    color: var(--primary-color);
    text-decoration: none;
    transition: text-decoration .2s;
}

footer a:hover {
    text-decoration: underline;
}

#certificate-container {
    display: none;
    position: relative;
    width: 297mm;
    height: 210mm;
    text-align: center;
    color: #383838;
    font-family: 'Times New Roman', Times, serif;
    overflow: hidden;
}

.certificate-bg {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 1;
    opacity: .9;
}

#cert-content {
    position: relative;
    z-index: 2;
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    padding: 20mm;
    box-sizing: border-box;
}

.cert-title {
    font-size: 28pt;
    font-weight: 700;
    color: #036;
    margin: 0;
}

.cert-subtitle {
    font-size: 16pt;
    border-bottom: 2px solid #555;
    padding-bottom: 10px;
    margin-bottom: 15mm;
    display: inline-block;
}

.cert-body {
    font-size: 14pt;
    margin: 3mm 0;
}

.cert-name {
    font-size: 18pt;
    font-weight: 700;
    color: #333;
    margin-bottom: 10mm;
    width: 80%;
    border-bottom: 1px dotted #777;
    padding-bottom: 5px;
}

#cert-line-1 {
    font-size: 24pt;
    font-weight: 700;
    color: #d35400;
    margin: 10px 0 15px 0;
}

#cert-line-2 {
    font-size: 18pt;
    margin-bottom: 10px;
}

#cert-line-3 {
    font-size: 14pt;
}

.cert-footer {
    position: absolute;
    bottom: 25mm;
    left: 0;
    width: 100%;
    padding: 0 30mm;
    box-sizing: border-box;
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    font-size: 12pt;
}

.cert-date,
.cert-signature {
    width: 40%;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

#history-list {
    list-style: none;
    padding: 0;
    text-align: left;
}

#history-list li {
    display: flex;
    justify-content: space-between;
    padding: 10px;
    border-bottom: 1px solid #f0f0f0;
}

#history-list li:last-child {
    border-bottom: none;
}

.question-slide-in {
    animation: slideIn .4s ease-out forwards;
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateX(30px);
    }

    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes pulse-effect {
    0% {
        transform: scale(1);
    }

    50% {
        transform: scale(1.03);
    }

    100% {
        transform: scale(1);
    }
}

@keyframes shine-effect {
    0% {
        transform: translateX(-100%) skewX(-30deg);
    }

    100% {
        transform: translateX(250%) skewX(-30deg);
    }
}

.progress-container {
    width: 100%;
    background-color: #e9ecef;
    border-radius: 20px;
    margin-bottom: 25px;
    position: relative;
    height: 22px;
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, .1);
    overflow: hidden;
}

.progress-bar {
    height: 100%;
    width: 0%;
    border-radius: 20px;
    background: linear-gradient(45deg, #28a745, #218838);
    position: relative;
    overflow: hidden;
    transition: width .5s cubic-bezier(.25, .8, .25, 1);
}

.progress-bar::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 50%;
    height: 100%;
    background: linear-gradient(to right, rgba(255, 255, 255, 0) 0, rgba(255, 255, 255, .3) 50%, rgba(255, 255, 255, 0) 100%);
    animation: shine-effect 2.5s infinite linear;
}

.progress-bar.progress-updated {
    animation: pulse-effect .5s ease-out;
}

.progress-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    color: #fff;
    font-weight: 700;
    font-size: .9em;
    text-shadow: 1px 1px 3px rgba(0, 0, 0, .6);
    white-space: nowrap;
}

body.dark-mode .progress-container {
    background-color: #374151;
}

@keyframes progress-bar-stripes {
    from {
        background-position: 40px 0;
    }

    to {
        background-position: 0 0;
    }
}

.category-button-group {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.category-button-group .exam-set-button {
    width: 100%;
    padding: 14px 10px;
    font-size: 1em;
    font-weight: 600;
    color: #fff;
    border: none;
    border-radius: 8px;
    text-align: center;
    cursor: pointer;
    transition: all .2s ease-in-out;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.category-button-group .learn-button {
    background-color: var(--warning-color);
}

.category-button-group .learn-button:hover {
    background-color: var(--warning-hover-color);
    transform: translateY(-2px);
}

.category-button-group>.exam-set-button:not(.learn-button) {
    background-color: var(--primary-color);
}

.category-button-group>.exam-set-button:not(.learn-button):hover {
    background-color: var(--primary-hover-color);
    transform: translateY(-2px);
}

.category-button-group .exam-set-button:disabled {
    cursor: not-allowed;
    opacity: .6;
    transform: none;
}

#clear-history-button {
    display: block;
    width: auto;
    min-width: 200px;
    padding: 12px 20px;
    margin: 20px auto 0;
    font-size: 1em;
    font-weight: 600;
    color: var(--white-color);
    background-color: var(--secondary-color);
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: all .2s ease-in-out;
    box-shadow: 0 2px 4px rgba(0, 0, 0, .1);
}

#clear-history-button:hover {
    background-color: var(--secondary-hover-color);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, .15);
}

#submit-quiz-button {
    display: block;
    width: 100%;
    margin-top: 25px;
    padding: 14px 20px;
    font-size: 1.1em;
    font-weight: 700;
    color: var(--white-color);
    background-color: var(--success-color);
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: all .2s ease-in-out;
    box-shadow: 0 2px 4px rgba(0, 0, 0, .1);
}

#submit-quiz-button:hover {
    background-color: var(--success-hover-color);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, .15);
}

#learning-options-list .option-item {
    padding: 12px 15px;
    background-color: #e9e9e9;
    border: 1px solid #e9e9e9;
    border-radius: 5px;
    margin-bottom: 10px;
    line-height: 1.4;
    transition: all .2s ease-in-out;
}

#learning-options-list .option-item.correct-choice {
    background-color: #d4edda !important;
    border-color: var(--success-color) !important;
    font-weight: 700;
    color: #155724;
    transform: scale(1.02);
}

#learning-answer-container .explanation-text {
    font-size: 1em;
    color: #333;
    font-style: normal;
}

.hamburger-menu .bar {
    transition: all .3s ease-in-out;
}

.hamburger-menu.active .bar:first-child {
    transform: translateY(8px) rotate(-45deg);
}

.hamburger-menu.active .bar:nth-child(2) {
    opacity: 0;
}

.hamburger-menu.active .bar:nth-child(3) {
    transform: translateY(-8px) rotate(45deg);
}

@media print {
    body>:not(.page-content-wrapper) {
        display: none !important;
    }

    .page-content-wrapper>:not(.quiz-container) {
        display: none !important;
    }

    .quiz-container>:not(#answer-review) {
        display: none !important;
    }

    #fb-comments-container {
        display: none !important;
    }

    #answer-review,
    .page-content-wrapper,
    .quiz-container {
        display: block !important;
        visibility: visible !important;
        box-shadow: none !important;
        border: none !important;
        margin: 0 !important;
        padding: 0 !important;
    }

    #answer-review * {
        color: #000 !important;
        background-color: #fff !important;
        visibility: visible !important;
    }

    .question-review-item {
        page-break-inside: avoid;
        border: 1px solid #ccc !important;
        padding: 15px !important;
        margin-bottom: 15px !important;
    }

    #answer-review .button-group {
        display: none !important;
    }

    body.printing-certificate>:not(#certificate-container) {
        display: none !important;
    }

    body.printing-certificate #certificate-container {
        display: block !important;
    }

    body.printing-certificate .certificate-bg {
        -webkit-print-color-adjust: exact !important;
        print-color-adjust: exact !important;
    }
}

.achievements-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(80px, 1fr));
    gap: 15px;
    margin-top: 15px;
}

.achievement-badge {
    position: relative;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 10px;
    border-radius: 8px;
    background-color: #f0f2f5;
    border: 1px solid var(--light-border);
    transition: all .3s ease;
    filter: grayscale(100%);
    opacity: .6;
}

.achievement-badge.unlocked {
    filter: grayscale(0%);
    opacity: 1;
    border-color: var(--warning-color);
    background-color: #fffbeb;
}

.achievement-icon {
    font-size: 2.5em;
}

.achievement-badge .tooltip-text {
    visibility: hidden;
    width: 160px;
    background-color: #333;
    color: #fff;
    text-align: center;
    border-radius: 6px;
    padding: 8px;
    position: absolute;
    z-index: 1;
    bottom: 115%;
    left: 50%;
    margin-left: -80px;
    opacity: 0;
    transition: opacity .3s;
}

.achievement-badge .tooltip-text::after {
    content: "";
    position: absolute;
    top: 100%;
    left: 50%;
    margin-left: -5px;
    border-width: 5px;
    border-style: solid;
    border-color: #333 transparent transparent transparent;
}

.achievement-badge.show-tooltip .tooltip-text,
.achievement-badge:hover .tooltip-text {
    visibility: visible;
    opacity: 1;
}

.achievement-toast {
    visibility: hidden;
    position: fixed;
    top: -100px;
    left: 50%;
    transform: translateX(-50%);
    z-index: 2000;
    white-space: nowrap;
    min-width: 250px;
    text-align: center;
    background-color: var(--success-color);
    color: #fff;
    padding: 16px 25px;
    border-radius: 8px;
    font-size: 1.1em;
    font-weight: 600;
    box-shadow: 0 4px 15px rgba(0, 0, 0, .2);
    transition: top .5s ease-in-out;
}

.achievement-toast.show {
    visibility: visible;
    top: 20px;
}

.fb-share-box {
    text-align: center;
    padding-bottom: 25px;
    margin-bottom: 25px;
    border-bottom: 1px solid var(--light-border);
}

.fb-share-box p {
    font-size: 1.1em;
    font-weight: 500;
    color: #4b4f56;
    margin-top: 0;
    margin-bottom: 15px;
}

body.dark-mode #fb-comments-container {
    background-color: #fff;
    border-radius: 8px;
    padding: 1px 15px 15px 15px;
    margin-top: 20px;
}

body.dark-mode #fb-comments-container .fb-share-box p,
body.dark-mode #fb-comments-container h2 {
    color: #1c1e21;
}

.image-modal {
    position: fixed;
    z-index: 2000;
    padding-top: 20px;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    overflow: auto;
    background-color: rgba(0, 0, 0, .9);
    display: flex;
    justify-content: center;
    align-items: center;
}

.modal-content {
    margin: auto;
    display: block;
    width: 90%;
    max-width: 800px;
    max-height: 90vh;
    object-fit: contain;
}

.close-modal-btn {
    position: absolute;
    top: 15px;
    right: 35px;
    color: #f1f1f1;
    font-size: 40px;
    font-weight: 700;
    transition: .3s;
    cursor: pointer;
}

.close-modal-btn:focus,
.close-modal-btn:hover {
    color: #bbb;
    text-decoration: none;
}

#question-timer-container {
    position: absolute;
    top: 85px;
    right: 25px;
    width: 45px;
    height: 45px;
    background-color: #f8d7da;
    color: var(--danger-color);
    border: 2px solid var(--danger-color);
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.4em;
    font-weight: 700;
}

.mode-selector-container {
    display: flex;
    border: 1px solid #ccc;
    border-radius: 8px;
    overflow: hidden;
    width: 100%;
    margin-bottom: 20px;
}

.mode-selector-container input[type=radio] {
    display: none;
}

.mode-selector-container label {
    flex: 1;
    padding: 12px 10px;
    text-align: center;
    font-weight: 600;
    cursor: pointer;
    background-color: #f0f2f5;
    color: var(--secondary-color);
    transition: all .3s ease;
    user-select: none;
}

.mode-selector-container input[type=radio]:checked+label {
    background-color: var(--primary-color);
    color: var(--white-color);
    box-shadow: inset 0 2px 4px rgba(0, 0, 0, .1);
}

.category-button-group .exam-set-button {
    background-color: var(--success-color);
}

.category-button-group .exam-set-button:hover {
    background-color: var(--success-hover-color);
}

#learning-options-list .option-item {
    cursor: pointer;
    transition: background-color .2s, border-color .2s;
}

#learning-options-list .option-item:hover {
    background-color: #dcdcdc;
    border-color: #b0b0b0;
}

#learning-options-list.answered .option-item {
    cursor: default;
    pointer-events: none;
    opacity: .7;
}

#learning-options-list .option-item.selected.correct {
    background-color: #d4edda !important;
    border-color: var(--success-color) !important;
    color: #155724;
    opacity: 1;
    font-weight: 700;
}

#learning-options-list .option-item.selected.wrong {
    background-color: #f8d7da !important;
    border-color: var(--danger-color) !important;
    color: #721c24;
    opacity: 1;
    font-weight: 700;
}

#learning-options-list .option-item.correct-answer-reveal {
    background-color: #d4edda !important;
    border-color: var(--success-color) !important;
    color: #155724;
    opacity: 1;
    font-weight: 700;
}

.button-group button,
.guidelines,
.mode-selector-container label,
.option-item label,
.quiz-container,
body,
nav {
    transition: background-color .3s ease, color .3s ease, border-color .3s ease;
}

body.dark-mode {
    --primary-color: #0d6efd;
    --primary-hover-color: #3385fd;
    --secondary-color: #4b5563;
    --secondary-hover-color: #6b7280;
    --success-color: #16a34a;
    --success-hover-color: #15803d;
    --danger-color: #ef4444;
    --warning-color: #f59e0b;
    --warning-hover-color: #d97706;
    --light-bg: #1f2937;
    --light-border: #374151;
    --text-color: #e5e7eb;
    --white-color: #111827;
    --body-bg: #111827;
}

body.dark-mode h1,
body.dark-mode h2,
body.dark-mode h3 {
    color: #f9fafb;
}

body.dark-mode .main-title-container h1 {
    color: #f9fafb;
}

body.dark-mode .option-item label {
    background-color: #374151;
    border-color: #4b5563;
}

body.dark-mode .option-item label:hover {
    background-color: #4b5563;
    border-color: #6b7280;
}

body.dark-mode .custom-radio {
    background-color: #1f2937;
    border-color: #9ca3af;
}

body.dark-mode .paging-tab,
body.dark-mode .question-nav-menu {
    background-color: #374151;
}

body.dark-mode .question-nav-item {
    background-color: #1f2937;
    border-color: #4b5563;
}

body.dark-mode .mode-selector-container {
    border-color: #4b5563;
}

body.dark-mode .mode-selector-container label {
    background-color: #374151;
}

body.dark-mode .mode-selector-container input[type=radio]:checked+label {
    background-color: var(--primary-color);
    color: #f9fafb;
}

.theme-switch-wrapper {
    display: flex;
    align-items: center;
    margin-left: 15px;
}

#sound-toggle-button,
#theme-toggle-button,
#vibration-toggle-button {
    background: 0 0;
    border: 2px solid var(--light-border);
    border-radius: 20px;
    cursor: pointer;
    font-size: 1.2rem;
    padding: 6px 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all .3s ease;
}

#sound-toggle-button {
    margin-right: 10px;
}

#sound-toggle-button:hover,
#theme-toggle-button:hover,
#vibration-toggle-button:hover {
    border-color: var(--primary-color);
}

#vibration-toggle-button {
    margin-right: 10px;
}

#theme-toggle-button .icon-moon {
    display: none;
}

body.dark-mode #theme-toggle-button .icon-moon {
    display: inline-block;
}

body.dark-mode #theme-toggle-button .icon-sun {
    display: none;
}

body.dark-mode .review-question-item {
    color: var(--text-color);
    background-color: var(--secondary-color);
    border-color: var(--secondary-hover-color);
}

body.dark-mode .review-question-item.answered {
    background-color: var(--success-hover-color);
    border-color: var(--success-color);
}

body.dark-mode .review-question-item.unanswered {
    background-color: var(--danger-color);
    border-color: #c82333;
}

body.dark-mode .review-question-item.current {
    background-color: var(--primary-color);
    border-color: var(--primary-hover-color);
    color: #fff;
}

body.dark-mode #learning-options-list .option-item {
    background-color: var(--secondary-color);
    border-color: var(--secondary-hover-color);
    color: var(--text-color);
}

body.dark-mode #learning-options-list .option-item:hover {
    background-color: var(--secondary-hover-color);
}

body.dark-mode #learning-options-list .option-item.selected.correct {
    background-color: var(--success-hover-color) !important;
    border-color: var(--success-color) !important;
    color: #fff !important;
}

body.dark-mode #learning-options-list .option-item.selected.wrong {
    background-color: var(--danger-color) !important;
    border-color: #c82333 !important;
    color: #fff !important;
}

body.dark-mode #learning-options-list .option-item.correct-answer-reveal {
    background-color: var(--success-hover-color) !important;
    border-color: var(--success-color) !important;
    color: #fff !important;
}

body.dark-mode .explanation-text {
    color: #b0b8c4 !important;
    border-top-color: var(--light-border) !important;
}

body.dark-mode .question-review-item .question-text-review {
    color: #cad1db;
}

body.dark-mode .question-review-item.throttling-question {
    color: #554200;
}

body.dark-mode .question-review-item.throttling-question .explanation-text,
body.dark-mode .question-review-item.throttling-question .question-text-review {
    color: inherit;
}

body.dark-mode .question-review-item.throttling-question .correct-answer {
    color: var(--success-color) !important;
}

body.dark-mode .question-review-item.throttling-question .your-answer.wrong {
    color: var(--danger-color) !important;
}

@keyframes slide-in-from-right {
    from {
        opacity: 0;
        transform: translateX(50px);
    }

    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes slide-in-from-left {
    from {
        opacity: 0;
        transform: translateX(-50px);
    }

    to {
        opacity: 1;
        transform: translateX(0);
    }
}

.animate-slide-in-right {
    animation: slide-in-from-right .4s ease-out forwards;
}

.animate-slide-in-left {
    animation: slide-in-from-left .4s ease-out forwards;
}

@keyframes shake-horizontal {

    0%,
    100% {
        transform: translateX(0);
    }

    10%,
    30%,
    50%,
    70%,
    90% {
        transform: translateX(-8px);
    }

    20%,
    40%,
    60%,
    80% {
        transform: translateX(8px);
    }
}

.animate-shake {
    animation: shake-horizontal .6s cubic-bezier(.36, .07, .19, .97) both;
}

.learning-correct-pulse {
    animation: pulse-green .7s;
}

@keyframes pulse-green {
    0% {
        box-shadow: 0 0 0 0 rgba(40, 167, 69, .7);
    }

    70% {
        box-shadow: 0 0 0 12px rgba(40, 167, 69, 0);
    }

    100% {
        box-shadow: 0 0 0 0 rgba(40, 167, 69, 0);
    }
}

#back-to-selection-button {
    background-color: #6c757d;
    flex-grow: 0.5;
}

#back-to-selection-button:hover {
    background-color: #5a6268;
}

#history-list li.history-item-hidden {
    display: none;
}

#history-container.expanded #history-list li.history-item-hidden {
    display: block;
    animation: fadeIn .4s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

#show-more-history {
    display: block;
    width: auto;
    min-width: 150px;
    padding: 8px 16px;
    margin: 15px auto 10px;
    font-size: .9em;
    font-weight: 600;
    color: var(--primary-color);
    background-color: transparent;
    border: 2px solid var(--primary-color);
    border-radius: 20px;
    cursor: pointer;
    transition: all .2s ease-in-out;
    text-align: center;
}

#show-more-history:hover {
    background-color: var(--primary-color);
    color: var(--white-color);
}

#show-more-history span {
    margin-right: 8px;
    font-size: 1.1em;
}

#desktop-button-group {
    display: flex;
}

@keyframes pulse-blue {
    0% {
        box-shadow: 0 0 0 0 rgba(0, 123, 255, .6);
    }

    70% {
        box-shadow: 0 0 0 12px rgba(0, 123, 255, 0);
    }

    100% {
        box-shadow: 0 0 0 0 rgba(0, 123, 255, 0);
    }
}

.learning-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    position: relative;
    padding: 0 10px;
}

.learning-header h2 {
    flex-grow: 1;
    text-align: center;
    margin: 0;
}

.learning-feedback-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, .6);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1001;
    opacity: 0;
    visibility: hidden;
    transition: opacity .3s ease, visibility .3s ease;
}

.learning-feedback-overlay.is-visible {
    opacity: 1;
    visibility: visible;
}

.feedback-content {
    background-color: #fff;
    width: calc(100% - 40px);
    max-width: 400px;
    padding: 24px;
    border-radius: 16px;
    text-align: center;
    box-shadow: 0 5px 20px rgba(0, 0, 0, .2);
    transform: scale(.95);
    transition: transform .3s cubic-bezier(.25, .8, .25, 1);
}

.learning-feedback-overlay.is-visible .feedback-content {
    transform: scale(1);
}

.learning-feedback-overlay.correct .feedback-content {
    background-color: #f0fff4;
    border: 1px solid #c3e6cb;
    color: #155724;
}

.learning-feedback-overlay.incorrect .feedback-content {
    background-color: #fff5f5;
    border: 1px solid #f5c6cb;
    color: #721c24;
}

.feedback-content #feedback-icon {
    font-size: 36px;
    line-height: 1;
}

.feedback-content h3 {
    margin-top: 8px;
    margin-bottom: 12px;
}

.feedback-content #feedback-explanation {
    margin-top: 10px;
    font-size: 1em;
    font-style: normal;
    line-height: 1.6;
}

#feedback-continue-btn {
    width: 100%;
    padding: 14px;
    margin-top: 24px;
    border: none;
    border-radius: 10px;
    font-size: 16px;
    font-weight: 700;
    color: #fff;
    cursor: pointer;
    transition: filter .2s;
}

#feedback-continue-btn:hover {
    filter: brightness(90%);
}

.correct #feedback-continue-btn {
    background-color: #28a745;
}

.incorrect #feedback-continue-btn {
    background-color: #dc3545;
}

@keyframes pulse-blue {
    0% {
        box-shadow: 0 0 0 0 rgba(0, 123, 255, .6);
    }

    70% {
        box-shadow: 0 0 0 12px rgba(0, 123, 255, 0);
    }

    100% {
        box-shadow: 0 0 0 0 rgba(0, 123, 255, 0);
    }
}

#start-smart-review-btn {
    background-color: #28a745 !important;
    color: #fff !important;
    border: none !important;
    border-radius: 8px !important;
    padding: 12px 20px !important;
    font-size: 1.1em !important;
    font-weight: 700 !important;
    cursor: pointer !important;
    transition: all .2s ease-in-out !important;
    box-shadow: 0 4px 10px rgba(40, 167, 69, .3) !important;
    margin-top: 15px !important;
}

#start-smart-review-btn:hover {
    background-color: #218838 !important;
    box-shadow: 0 6px 15px rgba(40, 167, 69, .4) !important;
    transform: translateY(-2px) !important;
}

#start-smart-review-btn:active {
    transform: translateY(0) !important;
    box-shadow: 0 2px 5px rgba(40, 167, 69, .3) !important;
}

.guidelines-split {
    display: flex;
    align-items: center;
    gap: 25px;
}

.guidelines-split-text {
    flex: 2;
}

.guidelines-split-animation {
    flex: 1;
    min-width: 250px;
}

.learning-header {
    position: relative;
}

.exit-learning-button-new {
    position: absolute;
    top: 50%;
    right: 15px;
    left: auto;
    transform: translateY(-50%);
    width: 40px;
    height: 40px;
    border-radius: 50%;
    font-size: 24px;
    font-weight: 700;
    line-height: 1;
    cursor: pointer;
    border: 2px solid;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform .2s ease;
}

.exit-learning-button-new:hover {
    transform: translateY(-50%) scale(1.1);
}

@keyframes traffic-light {
    0% {
        background-color: #f8d7da;
        color: #d9534f;
        border-color: #d9534f;
    }

    30% {
        background-color: #fff3cd;
        color: #856404;
        border-color: #ffeeba;
    }

    60% {
        background-color: #d4edda;
        color: #155724;
        border-color: #c3e6cb;
    }

    100% {
        background-color: #f8d7da;
        color: #d9534f;
        border-color: #d9534f;
    }
}

.exit-learning-button-animated {
    animation: traffic-light 3s infinite ease-in-out;
}

.loader-overlay {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(255, 255, 255, .8);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    z-index: 1010;
    border-radius: 8px;
    transition: opacity .3s ease;
}

.loader {
    border: 5px solid #f3f3f3;
    border-top: 5px solid var(--primary-color);
    border-radius: 50%;
    width: 50px;
    height: 50px;
    animation: spin 1s linear infinite;
}

.loader-overlay p {
    margin-top: 15px;
    font-weight: 500;
    color: var(--text-color);
}

@keyframes spin {
    0% {
        transform: rotate(0);
    }

    100% {
        transform: rotate(360deg);
    }
}

body.dark-mode .loader-overlay {
    background-color: rgba(17, 24, 39, .85);
}

.btn-disabled {
    opacity: .5;
    cursor: not-allowed !important;
    pointer-events: none;
}

.review-pagination {
    display: flex;
    justify-content: center;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 20px;
}

.pagination-tab {
    padding: 8px 16px;
    border: 1px solid #ccc;
    background-color: #f0f0f0;
    color: var(--text-color);
    border-radius: 20px;
    cursor: pointer;
    font-size: .9em;
    font-weight: 500;
    transition: all .2s ease;
}

.pagination-tab:hover {
    background-color: #e0e0e0;
    border-color: #a0a0a0;
}

.pagination-tab.active {
    background-color: var(--primary-color);
    color: #fff;
    border-color: var(--primary-color);
    font-weight: 700;
}

body.dark-mode .pagination-tab {
    background-color: #374151;
    border-color: #4b5563;
}

body.dark-mode .pagination-tab:hover {
    background-color: #4b5563;
}

body.dark-mode .pagination-tab.active {
    background-color: var(--primary-color);
    color: #f9fafb;
}

.search-container {
    display: flex;
    gap: 10px;
    margin: 15px 0 25px 0;
}

#search-input {
    flex-grow: 1;
    padding: 10px 15px;
    font-size: 1em;
    border: 1px solid var(--light-border);
    border-radius: 8px;
    background-color: var(--white-color);
    color: var(--text-color);
}

#search-button {
    flex-shrink: 0;
    padding: 0 18px;
    font-size: 1.2em;
    background-color: var(--primary-color);
    color: #fff;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: background-color .2s;
}

#search-button:hover {
    background-color: var(--primary-hover-color);
}

body.dark-mode #search-input {
    background-color: #374151;
    border-color: #4b5563;
}

.speed-run-button {
    background-color: var(--warning-color) !important;
    border: 2px solid var(--warning-hover-color) !important;
    box-shadow: 0 4px 15px rgba(243, 156, 18, .3) !important;
}

.speed-run-button:hover {
    background-color: var(--warning-hover-color) !important;
}

@keyframes pulse-red {
    0% {
        transform: scale(1);
        box-shadow: 0 0 0 0 rgba(220, 53, 69, .7);
    }

    70% {
        transform: scale(1.05);
        box-shadow: 0 0 0 10px rgba(220, 53, 69, 0);
    }

    100% {
        transform: scale(1);
        box-shadow: 0 0 0 0 rgba(220, 53, 69, 0);
    }
}

body.speed-run-active .timer {
    color: var(--danger-color);
    font-size: 1.5em;
    animation: pulse-red 1.5s infinite;
    padding: 5px 10px;
    border-radius: 8px;
    background-color: #f8d7da;
}

body.dark-mode.speed-run-active .timer {
    background-color: rgba(220, 53, 69, .2);
}

@keyframes traffic-light-effect {
    0% {
        background-color: #28a745;
        box-shadow: 0 0 10px #28a745;
    }

    33% {
        background-color: #f39c12;
        box-shadow: 0 0 10px #f39c12;
    }

    66% {
        background-color: #dc3545;
        box-shadow: 0 0 10px #dc3545;
    }

    100% {
        background-color: #28a745;
        box-shadow: 0 0 10px #28a745;
    }
}

#show-features-btn.animated-traffic-light {
    color: #fff !important;
    border: none;
    animation: traffic-light-effect 6s infinite linear;
    transition: transform .2s ease;
    height: 40px;
    border-radius: 5px;
    font-size: 1em;
}

#show-features-btn.animated-traffic-light:hover {
    transform: scale(1.03);
}

.features-popup-custom {
    padding: 10px !important;
}

.features-popup-custom .swal2-title {
    font-size: 1.8em !important;
    color: var(--primary-color);
    padding-top: 20px !important;
}

.features-popup-custom .swal2-html-container {
    margin: 0 !important;
    padding: 0 !important;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
    text-align: left;
    padding: 20px;
}

.feature-card {
    background-color: var(--body-bg);
    padding: 25px;
    border-radius: 12px;
    border: 1px solid var(--light-border);
    box-shadow: 0 4px 15px rgba(0, 0, 0, .05);
    transition: transform .2s ease, box-shadow .2s ease;
}

.feature-card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0, 0, 0, .1);
}

.feature-card h4 {
    font-size: 1.2em;
    color: var(--primary-hover-color);
    margin-top: 0;
    margin-bottom: 20px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.feature-card ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

.feature-card li {
    display: flex;
    align-items: flex-start;
    gap: 12px;
    margin-bottom: 12px;
    line-height: 1.5;
}

.feature-icon {
    font-size: 1.2em;
    flex-shrink: 0;
    margin-top: 2px;
}

body.dark-mode #fb-comments-container {
    background-color: #fff;
    border-radius: 8px;
    padding: 1px 15px 15px 15px;
    margin-top: 20px;
}

body.dark-mode #fb-comments-container h2 {
    color: #1c1e21;
}

body.dark-mode #smart-review-container .guidelines h3,
body.dark-mode #smart-review-container .guidelines p {
    color: #555;
}

a.exam-set-button {
    text-decoration: none;
    display: block;
    box-sizing: border-box;
}

.youtube-lazy-load-container {
    position: relative;
    width: 100%;
    padding-top: 56.25%;
    cursor: pointer;
    background-color: #000;
    overflow: hidden;
}

.youtube-lazy-load-container img {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform .3s ease;
}

.youtube-lazy-load-container:hover img {
    transform: scale(1.05);
}

.play-button-overlay {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 80px;
    height: 56px;
    transition: transform .2s ease;
    pointer-events: none;
}

.youtube-lazy-load-container:hover .play-button-overlay {
    transform: translate(-50%, -50%) scale(1.15);
}

.contact-popup {
    font-size: clamp(16px, 1rem + .1vw, 17px) !important;
}

.contact-popup .contact-popup-title {
    color: var(--primary-color) !important;
    font-weight: 600 !important;
}

.contact-popup .contact-popup-html-container {
    margin-top: 0 !important;
    text-align: left !important;
    overflow: hidden !important;
}

.contact-popup .contact-info-list {
    list-style: none;
    padding: 0;
    margin: 20px 0 0 0;
}

.contact-popup .contact-info-list li {
    display: flex;
    align-items: flex-start;
    margin-bottom: 16px;
    line-height: 1.6;
}

.contact-popup .contact-info-list .icon {
    font-size: 1.5em;
    margin-right: 18px;
    margin-top: -3px;
    color: var(--primary-hover-color);
    flex-shrink: 0;
}

.contact-popup .contact-info-list a {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    transition: color .2s ease;
}

.contact-popup .contact-info-list a:hover {
    color: var(--primary-hover-color);
    text-decoration: underline;
}

.contact-popup .contact-separator {
    height: 1px;
    background-color: var(--light-border);
    margin-top: 20px !important;
    margin-bottom: 20px !important;
    padding: 0 !important;
}

.guide-popup .swal2-html-container {
    text-align: left;
    line-height: 1.7;
}

.guide-popup .guide-image {
    max-width: 100%;
    height: auto;
    border-radius: 8px;
    margin: 15px 0;
    border: 1px solid #ddd;
    display: block;
    margin-left: auto;
    margin-right: auto;
}

body.dark-mode .guide-popup .guide-image {
    border-color: #4b5563;
}

.feedback-actions {
    margin-top: 20px;
    padding-top: 15px;
    border-top: 1px dashed #ccc;
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: .9em;
    color: #666;
}

body.dark-mode .feedback-actions {
    border-top-color: var(--light-border);
    color: #a0a0a0;
}

.feedback-btn {
    background: 0 0;
    border: 1px solid #ccc;
    border-radius: 50%;
    width: 32px;
    height: 32px;
    cursor: pointer;
    font-size: 1.1em;
    transition: all .2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
}

body.dark-mode .feedback-btn {
    border-color: var(--light-border);
}

.feedback-btn:hover {
    transform: scale(1.1);
    border-color: var(--primary-color);
}

.feedback-btn:disabled {
    cursor: not-allowed;
    opacity: .5;
    transform: none;
    border-color: #ccc !important;
}

.share-question-btn {
    background-color: #f0f0f0;
    color: #333;
    border: 1px solid #ccc;
    border-radius: 20px;
    padding: 5px 12px;
    cursor: pointer;
    font-size: .85em;
    font-weight: 500;
    margin-left: auto;
    transition: all .2s ease;
}

.share-question-btn:hover {
    background-color: #e0e0e0;
    border-color: #999;
}

body.dark-mode .share-question-btn {
    background-color: var(--secondary-color);
    border-color: var(--secondary-hover-color);
    color: var(--text-color);
}

.swal2-container.swal2-backdrop-show {
    background: rgba(0, 0, 0, .4) !important;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
}

.swal2-popup {
    border-radius: 20px !important;
    padding: 2em !important;
    box-shadow: 0 10px 30px rgba(0, 0, 0, .2), 0 0 0 1px rgba(0, 0, 0, .05) !important;
}

.swal2-popup.popup-correct {
    background: linear-gradient(145deg, #f0fff4, #d4edda) !important;
    border: 1px solid #a3e6cb !important;
}

.swal2-popup.popup-correct .swal2-title {
    color: #14532d !important;
}

.swal2-popup.popup-correct .swal2-html-container {
    color: #166534 !important;
    font-size: 1.1em !important;
    line-height: 1.7 !important;
    width: 100%;
    text-align: left;
    padding-left: 1px;
}

.swal2-popup.popup-correct .swal2-confirm {
    background: linear-gradient(to bottom, #28a745, #218838) !important;
    box-shadow: 0 4px 0 0 #15803d !important;
}

.swal2-popup.popup-incorrect {
    background: linear-gradient(145deg, #fff5f5, #f8d7da) !important;
    border: 1px solid #f5c6cb !important;
}

.swal2-popup.popup-incorrect .swal2-title {
    color: #7f1d1d !important;
}

.swal2-popup.popup-incorrect .swal2-html-container {
    color: #991b1b !important;
    font-size: 1.1em !important;
    line-height: 1.7 !important;
    width: 100%;
    text-align: left;
    padding-left: 1px;
}

#learning-mobile-share-btn {
    background-color: #6c757d !important;
    color: #fff !important;
}

#learning-mobile-share-btn svg {
    stroke: white !important;
}

#learning-mobile-share-btn:hover {
    background-color: #5a6268 !important;
}

body.dark-mode #learning-mobile-share-btn {
    background-color: #4b5563 !important;
}

body.dark-mode #learning-mobile-share-btn:hover {
    background-color: #6b7280 !important;
}

.swal2-popup.popup-incorrect .swal2-confirm {
    background: linear-gradient(to bottom, #dc3545, #c82333) !important;
    box-shadow: 0 4px 0 0 #b91c1c !important;
}

.swal2-title {
    font-size: 2em !important;
    font-weight: 700 !important;
    padding: .5em 0 !important;
}

.swal2-confirm {
    border: none !important;
    border-radius: 12px !important;
    padding: .8em 2em !important;
    font-size: 1.1em !important;
    font-weight: 600 !important;
    color: #fff !important;
    transform: translateY(0);
    transition: all .15s ease-out !important;
}

.swal2-confirm:hover {
    filter: brightness(110%);
    transform: translateY(-2px);
}

.swal2-confirm:active {
    transform: translateY(1px);
    filter: brightness(100%);
    box-shadow: 0 2px 0 0 rgba(0, 0, 0, .2) !important;
}

.swal2-container.swal2-backdrop-show {
    background: rgba(0, 0, 0, .4) !important;
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
}

.swal2-popup {
    display: flex !important;
    flex-direction: column !important;
    background: #fff !important;
    border-radius: 20px !important;
    padding: 1.5em 2em 2em 2em !important;
    box-shadow: 0 10px 30px rgba(0, 0, 0, .1), 0 0 0 1px rgba(0, 0, 0, .05) !important;
    border: 1px solid rgba(0, 0, 0, .05) !important;
    width: 90vw !important;
    max-width: 100%;
}

.swal2-title {
    font-size: clamp(1.5em, 5vw, 1.8em) !important;
    font-weight: 700 !important;
    padding: .5em 0 !important;
    color: #333 !important;
    line-height: 1.3 !important;
}

.swal2-html-container {
    font-size: clamp(1em, 4vw, 1.1em) !important;
    line-height: 1.7 !important;
    color: #555 !important;
    margin: 0 0 1.5em 0 !important;
    text-align: left !important;
}

.swal2-html-container p {
    margin: 0 0 10px 0 !important;
}

.swal2-html-container strong {
    color: #333;
}

.swal2-actions {
    gap: 1em !important;
}

.swal2-styled {
    border-radius: 12px !important;
    padding: .8em 2em !important;
    font-size: 1em !important;
    font-weight: 600 !important;
    transform: translateY(0);
    transition: all .2s ease-out !important;
    box-shadow: 0 2px 5px rgba(0, 0, 0, .1) !important;
    border: none !important;
}

.swal2-styled:hover {
    transform: translateY(-2px);
    filter: brightness(105%);
}

.swal2-styled:active {
    transform: translateY(0);
    filter: brightness(100%);
    box-shadow: 0 1px 2px rgba(0, 0, 0, .1) !important;
}

.swal2-confirm {
    background: linear-gradient(to top, #007bff, #0d6efd) !important;
    color: #fff !important;
}

.swal2-cancel {
    background: #e9ecef !important;
    color: #495057 !important;
}

.swal2-popup.popup-correct {
    background: linear-gradient(145deg, #f0fff4, #e6f7ec) !important;
}

.swal2-popup.popup-correct .swal2-title {
    color: #14532d !important;
}

.swal2-popup.popup-correct .swal2-html-container {
    color: #166534 !important;
}

.swal2-popup.popup-correct .swal2-confirm {
    background: linear-gradient(to top, #28a745, #218838) !important;
}

.swal2-popup.popup-incorrect {
    background: linear-gradient(145deg, #fff5f5, #fdeded) !important;
}

.swal2-popup.popup-incorrect .swal2-title {
    color: #7f1d1d !important;
}

.swal2-popup.popup-incorrect .swal2-html-container {
    color: #991b1b !important;
}

.swal2-popup.popup-incorrect .swal2-confirm {
    background: linear-gradient(to top, #dc3545, #c82333) !important;
}

.swal2-icon {
    margin: 1em auto .5em auto !important;
    border-width: .2em !important;
}

body.dark-mode .swal2-popup {
    background: #2c2c32 !important;
    color: #e5e7eb !important;
    border: 1px solid rgba(255, 255, 255, .1) !important;
    box-shadow: 0 10px 30px rgba(0, 0, 0, .2) !important;
}

body.dark-mode .swal2-title {
    color: #fff !important;
}

body.dark-mode .swal2-html-container {
    color: #c7c7d2 !important;
}

body.dark-mode .swal2-html-container strong {
    color: #fff;
}

body.dark-mode .swal2-cancel {
    background: #4b5563 !important;
    color: #e5e7eb !important;
}

body.dark-mode .swal2-popup.popup-correct {
    background: linear-gradient(145deg, #052e16, #064e3b) !important;
}

body.dark-mode .swal2-popup.popup-incorrect {
    background: linear-gradient(145deg, #450a0a, #7f1d1d) !important;
}

body.dark-mode .swal2-popup.popup-correct .swal2-html-container,
body.dark-mode .swal2-popup.popup-correct .swal2-title,
body.dark-mode .swal2-popup.popup-incorrect .swal2-html-container,
body.dark-mode .swal2-popup.popup-incorrect .swal2-title {
    color: #fff !important;
}

.swal2-popup {
    max-width: 500px !important;
}

.swal2-toast.swal2-popup {
    width: auto !important;
    max-width: 380px !important;
    padding: 1em 1.2em !important;
    box-shadow: 0 5px 15px rgba(0, 0, 0, .15) !important;
    flex-direction: row !important;
    align-items: center !important;
    gap: 1em !important;
}

.swal2-toast .swal2-icon {
    width: 2.5em !important;
    height: 2.5em !important;
    margin: 0 !important;
    font-size: 1.2rem !important;
}

.swal2-toast .swal2-title {
    font-size: 1.1em !important;
    padding: 0 !important;
    text-align: left;
    color: #333 !important;
}

.swal2-toast .swal2-html-container {
    font-size: 1em !important;
    margin: 0 !important;
    padding: 0 !important;
    text-align: left;
    color: #555 !important;
}

.swal2-toast .swal2-html-container b {
    color: var(--primary-color);
}

.swal2-toast .swal2-actions,
.swal2-toast .swal2-footer {
    display: none !important;
}

.swal2-toast .swal2-timer-progress-bar {
    height: 5px !important;
    border-radius: 0 0 16px 16px;
    background-color: var(--primary-color) !important;
    opacity: .7;
}

body.dark-mode .swal2-toast.swal2-popup {
    background: #374151 !important;
    border-color: rgba(255, 255, 255, .1) !important;
}

body.dark-mode .swal2-toast .swal2-title {
    color: #f9fafb !important;
}

body.dark-mode .swal2-toast .swal2-html-container {
    color: #d1d5db !important;
}

body.dark-mode .swal2-toast .swal2-html-container b {
    color: #60a5fa;
}

.zalo-chat-bubble {
    position: fixed;
    bottom: 25px;
    right: 25px;
    width: 60px;
    height: 60px;
    background-color: #0068ff;
    border-radius: 50%;
    box-shadow: 0 4px 12px rgba(0, 0, 0, .2);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: transform .2s ease;
    z-index: 999;
}

.zalo-chat-bubble:hover {
    transform: scale(1.1);
}

.zalo-chat-bubble img {
    width: 32px;
    height: 32px;
}

#zalo-iframe-container {
    display: none;
    position: fixed;
    bottom: 25px;
    right: 25px;
    width: 350px;
    height: 420px;
    border: 1px solid #e5e5e5;
    border-radius: 8px;
    box-shadow: 0 5px 20px rgba(0, 0, 0, .2);
    overflow: hidden;
    z-index: 1000;
}

#zalo-iframe {
    width: 100%;
    height: 100%;
    border: none;
}

#zalo-close-btn {
    position: absolute;
    top: 5px;
    right: 5px;
    width: 24px;
    height: 24px;
    background-color: rgba(0, 0, 0, .3);
    color: #fff;
    border: none;
    border-radius: 50%;
    cursor: pointer;
    font-weight: 700;
    font-size: 14px;
    line-height: 24px;
    text-align: center;
    z-index: 1001;
}

body.zalo-chat-open .zalo-chat-bubble {
    display: none;
}

#personal-goal-container {
    border-left: 5px solid var(--primary-color);
    background-color: #f0f7ff;
    text-align: center;
}

body.dark-mode #personal-goal-container {
    background-color: #1f2937;
    border-left-color: var(--primary-hover-color);
}

#countdown-timer {
    font-size: 1.3em;
    font-weight: 700;
    color: var(--danger-color);
    margin-bottom: 15px;
    animation: pulse-red 2s infinite;
}

#exam-date-input {
    padding: 10px;
    border-radius: 8px;
    border: 1px solid var(--light-border);
    font-size: 1em;
    margin: 0 10px 10px 0;
    background-color: var(--white-color);
    color: var(--text-color);
}

#reset-goal-button,
#set-goal-button {
    width: auto;
    min-width: 150px;
    margin: 0 auto;
}

#reset-goal-button {
    background-color: var(--secondary-color) !important;
}

.exam-set-button {
    display: inline-block;
    padding: 10px 24px;
    font-size: 1em;
    font-weight: 600;
    color: #fff;
    border: none;
    border-radius: 8px;
    text-align: center;
    cursor: pointer;
    transition: all .2s ease-in-out;
    text-decoration: none;
    box-shadow: 0 2px 4px rgba(0, 0, 0, .1);
}

.exam-set-button:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, .15);
}

.exam-set-button:disabled {
    cursor: not-allowed;
    opacity: .6;
    transform: none;
    box-shadow: none;
}

#set-goal-button,
.category-button-group>.exam-set-button {
    background-color: var(--primary-color);
}

#set-goal-button:hover,
.category-button-group>.exam-set-button:hover {
    background-color: var(--primary-hover-color);
}

#reset-goal-button {
    background-color: var(--secondary-color) !important;
}

#reset-goal-button:hover {
    background-color: var(--secondary-hover-color) !important;
}

.swal2-popup.features-popup-custom {
    max-width: 1200px !important;
}

.swal2-popup.contact-popup {
    max-width: 700px !important;
}

.swal2-popup.guide-popup {
    max-width: 650px !important;
}

body.zalo-chat-hidden .zalo-chat-widget {
    display: none !important;
    visibility: hidden !important;
    opacity: 0 !important;
}

.swal2-popup.video-popup-fullscreen {
    width: 90vw !important;
    max-width: 90vw !important;
    padding: 1em !important;
}

.swal2-popup.video-popup-fullscreen .swal2-html-container {
    padding: 0;
    margin: 1em 0 0 0;
}

.swal2-container.custom-toast-container {
    pointer-events: none;
}

.swal2-popup.custom-toast-popup {
    padding: 1em !important;
    border-radius: 12px !important;
    width: auto !important;
    max-width: 400px !important;
    box-shadow: 0 5px 15px rgba(0, 0, 0, .15) !important;
    pointer-events: auto;
    display: flex !important;
    align-items: center !important;
}

.swal2-popup.custom-toast-popup .swal2-header {
    padding: 0 .5em !important;
}

.swal2-popup.custom-toast-popup .swal2-title {
    font-size: 1em !important;
}

.swal2-popup.custom-toast-popup .swal2-actions {
    margin: 0 0 0 1.5em !important;
}

#star-rating-container {
    display: flex;
    justify-content: center;
    font-size: 2.5em;
    cursor: pointer;
    color: #ccc;
}

.star:hover,
.star.hovered {
    color: #f39c12;
}

.star.rated {
    color: #f39c12;
}

#rating-feedback-text {
    text-align: center;
    font-weight: bold;
    color: var(--success-color);
    display: none;
    margin-top: 15px;
}

body.fullscreen-active #rating-section {
    display: none;
}

#review-mode-overlay #review-pagination {
    display: flex;
    justify-content: center;
    margin-bottom: 25px;
    border: 1px solid #dee2e6;
    border-radius: 8px;
    overflow: hidden;
    width: 100%;
    max-width: 450px;
    margin-left: auto;
    margin-right: auto;
    padding: 0;
}

#review-pagination .pagination-button {
    background-color: #ffffff;
    border: none;
    border-radius: 0;
    padding: 12px 18px;
    cursor: pointer;
    font-weight: 600;
    font-size: 1em;
    color: #555;
    transition: all 0.2s ease-in-out;
    flex-grow: 1;
    text-align: center;
    white-space: nowrap;
    margin: 0;
    outline: none;
}

#review-pagination .pagination-button:not(:last-child) {
    border-right: 1px solid #dee2e6;
}

#review-pagination .pagination-button:hover {
    background-color: #f8f9fa;
}

#review-pagination .pagination-button.active {
    background-color: var(--primary-color);
    color: white;
    cursor: default;
    font-weight: 700;
}

body.dark-mode #review-mode-overlay #review-pagination {
    border-color: #4b5563;
}

body.dark-mode #review-pagination .pagination-button {
    background-color: var(--white-color);
    color: #e5e7eb;
}

body.dark-mode #review-pagination .pagination-button:not(:last-child) {
    border-right-color: #4b5563;
}

body.dark-mode #review-pagination .pagination-button:hover {
    background-color: #374151;
}

body.dark-mode #review-pagination .pagination-button.active {
    background-color: var(--primary-color);
    color: white;
}

/* =================================================================== */
/* ==== CODE HOÀN CHỈNH CHO GIAO DIỆN DI ĐỘNG (ĐÃ TỐI ƯU) ==== */
/* =================================================================== */

@media (max-width: 768px) {
    /* ---- Cấu trúc chung ---- */
    body {
        padding: 0 10px;
        box-sizing: border-box;
    }

    .main-title-container,
    .nav-container,
    .quiz-container,
    footer {
        margin-left: 0;
        margin-right: 0;
        width: 100%;
    }

    .nav-container {
        margin-bottom: 0;
    }

    .main-title-container,
    .quiz-container,
    footer {
        margin-top: 15px;
    }

    .main-title-container h1 {
        font-size: 1.2em;
        padding: 0 10px;
    }

    /* ---- Header & Menu ---- */
    nav {
        padding: 10px 15px;
        position: relative;
        border-radius: 8px;
    }

    .mobile-header {
        display: flex;
        justify-content: space-between;
        align-items: center;
        width: 100%;
    }

    .mobile-title {
        font-weight: 600;
        font-size: 1.1em;
    }

    .hamburger-menu {
        display: block;
        padding: 8px;
        cursor: pointer;
    }

    .hamburger-menu .bar {
        width: 25px;
        height: 3px;
        background-color: var(--text-color);
        margin: 5px 0;
    }

    .menu-list {
        display: none;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        width: auto;
        background-color: var(--white-color);
        flex-direction: column;
        box-shadow: 0 4px 8px rgba(0, 0, 0, .1);
        padding: 0;
        z-index: 10;
        border: 1px solid #ccc;
        border-top: none;
        border-bottom-left-radius: 8px;
        border-bottom-right-radius: 8px;
    }

    .menu-list.show {
        display: flex;
    }

    .menu-item {
        width: 100%;
        text-align: center;
    }

    .menu-item a {
        padding: 15px;
        width: 100%;
        border-bottom: 1px solid #f0f0f0;
        box-sizing: border-box;
    }
    .menu-item:last-child a {
        border-bottom: none;
    }
    
    /* ---- Màn hình chọn & hướng dẫn ---- */
    .guidelines {
        font-size: 1em;
        padding: 15px;
    }
    .guidelines-flex {
        flex-direction: column;
        text-align: justify;
    }
    .guidelines-image {
        width: 100%;
    }
    .exam-sets-grid {
        grid-template-columns: 1fr;
        gap: 10px;
    }

    /* ---- Màn hình thi trắc nghiệm ---- */
    #quiz-main-screen {
        position: relative;
        padding-top: 80px; /* Thêm khoảng trống cho header dính */
    }

    #quiz-main-screen .quiz-header-mobile {
         position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        z-index: 100;
        background-color: var(--white-color);
        padding: 12px 15px;
        box-sizing: border-box;
        border-bottom: 1px solid var(--light-border);
        display: flex;
        align-items: center;
        gap: 15px;
    }
    
    #quiz-main-screen .quiz-header-mobile .progress-container {
        flex-grow: 1;
        margin-bottom: 0;
        height: 26px;
    }
    #quiz-main-screen .progress-text {
        font-size: 1em;
    }
    
    #quiz-main-screen .timer, .timer {
        position: static;
        margin-bottom: 0;
        flex-shrink: 0;
        text-align: center;
        font-size: 1.4em;
    }

    #question-text {
        font-size: 1.1em;
    }
    
    .option-item label {
        font-size: 1em;
        padding: 15px;
    }

    .button-group {
        flex-direction: column;
    }

    /* --- BẮT ĐẦU KHỐI MÃ SỬA LỖI FOOTER DI ĐỘNG --- */

/* 1. Mặc định: ẨN footer trên màn hình lớn (máy tính) */
.mobile-nav-footer {
    display: none !important;
}

/* 2. KHI màn hình nhỏ (<= 768px): HIỆN footer và định dạng nó */
@media (max-width: 768px) {
    #desktop-button-group {
        display: none;
    }
    .mobile-nav-footer {
        display: flex !important; /* Quan trọng: Ghi đè lệnh display:none ở trên */
        position: fixed !important;
        left: 50% !important;
        transform: translateX(-50%) !important;
        bottom: 10px !important;
        width: 95% !important;
        background-color: rgba(255, 255, 255, .9) !important;
        backdrop-filter: blur(10px);
        -webkit-backdrop-filter: blur(10px);
        border: 1px solid rgba(222, 226, 230, .7) !important;
        border-radius: 16px !important;
        align-items: center !important;
        justify-content: space-between !important;
        padding: 8px !important;
        gap: 8px;
        z-index: 1000 !important;
        box-shadow: 0 4px 20px rgba(0, 0, 0, .1) !important;
    }

    /* Định dạng cho các nút bên trong footer trên di động */
    .mobile-nav-btn {
        display: flex !important;
        align-items: center !important;
        justify-content: center !important;
        flex-direction: row !important;
        gap: 6px !important;
        height: 48px !important;
        padding: 0 16px !important;
        border: none !important;
        border-radius: 12px !important;
        font-size: 1em !important;
        font-weight: 600 !important;
        cursor: pointer !important;
        transition: all .2s ease-in-out !important;
        flex-grow: 1;
        white-space: nowrap;
        -webkit-tap-highlight-color: transparent;
    }

    .mobile-nav-btn span {
        display: none;
    }

    /* Nếu màn hình đủ rộng một chút thì hiện cả chữ */
    @media (min-width: 400px) {
        .mobile-nav-btn span {
            display: inline;
        }
    }
}

/* Class helper của Javascript để ẩn/hiện footer khi cần */
.mobile-nav-footer.is-hidden {
    display: none !important;
}


/* --- KẾT THÚC KHỐI MÃ SỬA LỖI --- */
    
    /* ---- Màn hình xem lại ---- */
    .review-mode-content {
        padding: 20px;
        width: 95%;
    }

    .review-question-grid {
        grid-template-columns: repeat(auto-fit, minmax(40px, 1fr));
    }
}
/* BỔ SUNG THÊM HAI QUY TẮC MỚI NÀY VÀO CUỐI FILE CSS */
.exam-sets-grid > .category-button-group {
  flex-grow: 1; /* Cho phép các nút co giãn */
  flex-basis: calc(50% - 8px); /* Chia thành 2 cột, trừ đi một nửa khoảng trống */
}

.exam-sets-grid > .category-button-group.is-wide {
  flex-basis: 100%; /* Dành cho các nút muốn chiếm trọn 1 hàng */

}
/* =================================================================== */
/* ==== BỘ QUY TẮC GHI ĐÈ CUỐI CÙNG ĐỂ SỬA LỖI HIỂN THỊ ==== */
/* =================================================================== */

/* 1. Mặc định, luôn ẩn thanh điều hướng di động trên mọi kích thước màn hình */
.mobile-nav-footer {
    display: none !important;
}

/* 2. Class is-hidden phải luôn có tác dụng ẩn */
.mobile-nav-footer.is-hidden {
    display: none !important;
}

/* 3. CHỈ KHI màn hình nhỏ VÀ KHÔNG CÓ class is-hidden thì mới hiện lên */
@media (max-width: 768px) {
    .mobile-nav-footer:not(.is-hidden) {
        display: flex !important;
    }

    /* 4. Đồng thời, trên màn hình nhỏ, luôn ẩn bộ nút của desktop */
    #desktop-button-group {
        display: none !important;
    }
}
/* ================================================= */
/* ==== ĐOẠN CODE CHẨN ĐOÁN & SỬA LỖI CUỐI CÙNG ==== */
/* ================================================= */

/* Nếu đoạn code này chạy, thanh footer sẽ CÓ NỀN ĐỎ */
.mobile-nav-footer {
    background-color: #027bff !important;
}

/* Luôn ẩn footer theo mặc định */
.mobile-nav-footer.is-hidden {
    display: none !important;
}

/* Trên di động, chỉ hiện footer khi KHÔNG có class is-hidden */
@media (max-width: 768px) {
    .mobile-nav-footer:not(.is-hidden) {
        display: flex !important;
    }

    /* Nếu đoạn code này chạy, các nút desktop sẽ BIẾN MẤT */
    /* Để chẩn đoán, nó cũng sẽ có viền đỏ nếu chưa biến mất */
    #desktop-button-group {
        display: none !important;
        border: 5px solid red !important;
    }
}