:root {
    --font-family-stack: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", "Liberation Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
    --font-size-base: 16px;
    --font-size-sm: 20px;
    --font-weight-base: 400;
    --line-height-base: 24px;
    --color-surface-base: #000000;
    --color-text-secondary: #212529;
    --color-text-tertiary: #ababab;
    --color-surface-muted: #ffffff;
    --color-surface-raised: #ff7b31;
    --color-surface-strong: #fff5ef;
    --color-border-strong: rgba(0, 0, 0, 0.125);
    --color-focus: rgba(255, 123, 49, 0.42);
    --color-success-bg: #e6f6ef;
    --color-success-border: #198754;
    --color-success-text: #0f5132;
    --color-error-bg: #fcebea;
    --color-error-border: #dc3545;
    --color-error-text: #842029;
    --color-warning-bg: #fff3cd;
    --color-warning-border: #ffb020;
    --color-warning-text: #664d03;
    --space-1: 4px;
    --space-2: 5px;
    --space-3: 6px;
    --space-4: 8px;
    --space-5: 12px;
    --space-6: 16px;
    --space-7: 24px;
    --space-8: 48px;
    --radius-xs: 3px;
    --radius-sm: 6px;
    --radius-md: 8px;
    --radius-lg: 12px;
    --shadow-1: rgba(46, 46, 46, 0.1) 0 0 8px 0;
    --motion-instant: 150ms;
    --motion-fast: 200ms;
    --z-sticky: 30;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
}

body {
    min-height: 100dvh;
    font-family: var(--font-family-stack);
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-base);
    line-height: var(--line-height-base);
    background: var(--color-surface-strong);
    color: var(--color-text-secondary);
    padding-bottom: 118px;
}

.skip-link {
    position: fixed;
    top: var(--space-5);
    left: var(--space-5);
    z-index: 50;
    transform: translateY(-160%);
    border-radius: var(--radius-md);
    background: var(--color-surface-base);
    color: var(--color-surface-muted);
    padding: var(--space-4) var(--space-5);
    font-weight: 700;
    text-decoration: none;
}

.skip-link:focus {
    transform: translateY(0);
}

main.app {
    width: min(100%, 960px);
    margin: 0 auto;
    padding: var(--space-7) var(--space-6) var(--space-8);
}

.hero {
    position: relative;
    overflow: hidden;
    isolation: isolate;
    min-height: 360px;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    border: 1px solid var(--color-border-strong);
    border-radius: var(--radius-lg);
    background:
        linear-gradient(90deg, rgba(0, 0, 0, 0.92) 0%, rgba(0, 0, 0, 0.72) 37%, rgba(0, 0, 0, 0.16) 72%),
        linear-gradient(180deg, rgba(0, 0, 0, 0.22) 0%, rgba(0, 0, 0, 0.68) 100%),
        url("hero-banner.png") center / cover no-repeat;
    padding: var(--space-7);
    margin-bottom: var(--space-7);
    box-shadow: var(--shadow-1);
}

.hero::after {
    content: "";
    position: absolute;
    inset: 0;
    z-index: -1;
    background: radial-gradient(circle at 18% 12%, rgba(255, 123, 49, 0.22), transparent 30%);
    pointer-events: none;
}

.brand-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: var(--space-6);
    margin-bottom: var(--space-6);
}

.brand-lockup {
    display: inline-flex;
    align-items: center;
    min-width: 0;
    border-radius: var(--radius-md);
    background: rgba(255, 255, 255, 0.94);
    padding: var(--space-3) var(--space-4);
    text-decoration: none;
    transition: background-color var(--motion-instant) ease, outline-color var(--motion-instant) ease;
}

.brand-lockup:hover {
    background: var(--color-surface-muted);
}

.brand-lockup:focus-visible {
    outline: 3px solid var(--color-focus);
    outline-offset: 2px;
}

.brand-logo {
    display: block;
    width: min(220px, 56vw);
    height: auto;
}

h1#quizTitle {
    max-width: 100%;
    margin-top: auto;
    color: var(--color-surface-muted);
    font-size: clamp(0.95rem, 4.85vw, 2.65rem);
    font-weight: 800;
    line-height: 1.15;
    letter-spacing: -0.02em;
    white-space: nowrap;
    text-shadow: 0 2px 16px rgba(0, 0, 0, 0.48);
}

.hero-copy {
    max-width: 65ch;
    margin-top: var(--space-5);
    color: var(--color-surface-strong);
    text-wrap: pretty;
    text-shadow: 0 1px 10px rgba(0, 0, 0, 0.5);
}

.quiz-info {
    display: flex;
    gap: var(--space-4);
    margin-top: var(--space-6);
    flex-wrap: wrap;
}

.info-tag {
    border: 1px solid rgba(255, 255, 255, 0.26);
    border-radius: 999px;
    background: rgba(255, 245, 239, 0.96);
    color: var(--color-surface-base);
    padding: var(--space-2) var(--space-5);
    font-weight: 700;
}

.notice {
    display: none;
    border: 1px solid var(--color-warning-border);
    border-radius: var(--radius-lg);
    background: var(--color-warning-bg);
    color: var(--color-warning-text);
    padding: var(--space-5) var(--space-6);
    margin-bottom: var(--space-6);
    font-weight: 700;
}

.notice.is-visible {
    display: block;
}

.sticky-status {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    z-index: var(--z-sticky);
    display: grid;
    grid-template-columns: minmax(280px, 1fr) auto auto;
    align-items: center;
    gap: var(--space-6);
    border-top: 1px solid var(--color-border-strong);
    background: var(--color-surface-muted);
    box-shadow: var(--shadow-1);
    padding: var(--space-5) var(--space-7);
}

.status-left {
    display: flex;
    align-items: center;
    gap: var(--space-6);
    min-width: 0;
}

.progress-container {
    display: flex;
    align-items: center;
    gap: var(--space-4);
    min-width: 0;
    flex: 1;
}

.progress-label {
    color: var(--color-text-secondary);
    font-weight: 700;
    white-space: nowrap;
}

progress {
    width: 100%;
    min-width: 140px;
    height: 10px;
    overflow: hidden;
    border: 0;
    border-radius: 999px;
    background-color: var(--color-surface-strong);
}

progress::-webkit-progress-bar {
    background-color: var(--color-surface-strong);
}

progress::-webkit-progress-value {
    background-color: var(--color-surface-raised);
}

progress::-moz-progress-bar {
    background-color: var(--color-surface-raised);
}

.timer-container {
    display: flex;
    align-items: center;
    gap: var(--space-4);
    border: 1px solid var(--color-border-strong);
    border-radius: var(--radius-md);
    background: var(--color-surface-strong);
    color: var(--color-text-secondary);
    padding: var(--space-3) var(--space-5);
    font-family: ui-monospace, SFMono-Regular, Consolas, Monaco, "Liberation Mono", monospace;
    font-weight: 800;
    font-variant-numeric: tabular-nums;
}

.timer-label {
    color: var(--color-text-secondary);
    font-size: 0.82rem;
    font-weight: 700;
}

.copyright {
    color: var(--color-text-secondary);
    font-size: 0.88rem;
    text-align: center;
    white-space: nowrap;
}

.copyright a {
    color: var(--color-text-secondary);
    font-weight: 800;
    text-decoration: underline;
    text-decoration-color: var(--color-surface-raised);
    text-underline-offset: 3px;
}

.footer-actions {
    display: flex;
    justify-content: flex-end;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 42px;
    border: 1px solid transparent;
    border-radius: var(--radius-md);
    padding: 10px var(--space-6);
    font: inherit;
    font-weight: 800;
    cursor: pointer;
    text-decoration: none;
    transition: background-color var(--motion-instant) ease, color var(--motion-instant) ease, border-color var(--motion-instant) ease, transform var(--motion-instant) ease;
}

.btn:hover {
    transform: translateY(-1px);
}

.btn:active {
    transform: translateY(1px);
}

.btn:focus-visible,
.option-label:focus-within {
    outline: 3px solid var(--color-focus);
    outline-offset: 2px;
}

.btn-primary {
    background-color: var(--color-surface-base);
    color: var(--color-surface-muted);
}

.btn-primary:hover {
    background-color: var(--color-surface-raised);
    color: var(--color-surface-base);
}

.btn-secondary {
    border-color: var(--color-border-strong);
    background-color: var(--color-surface-muted);
    color: var(--color-text-secondary);
}

.btn-secondary:hover {
    background-color: var(--color-surface-strong);
}

.btn:disabled {
    cursor: not-allowed;
    opacity: 0.6;
    transform: none;
}

.result-block {
    display: none;
    border: 1px solid var(--color-border-strong);
    border-radius: var(--radius-lg);
    background: var(--color-surface-muted);
    padding: var(--space-7);
    margin-bottom: var(--space-7);
    box-shadow: var(--shadow-1);
    animation: resultReveal var(--motion-fast) ease-out;
}

@keyframes resultReveal {
    from {
        opacity: 0;
        transform: translateY(-8px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.result-title {
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
    font-weight: 800;
    line-height: 1.3;
    text-align: center;
}

.result-stats {
    display: flex;
    justify-content: center;
    gap: var(--space-5);
    margin-top: var(--space-6);
    flex-wrap: wrap;
}

.stat-card {
    min-width: 128px;
    border: 1px solid var(--color-border-strong);
    border-radius: var(--radius-lg);
    background: var(--color-surface-strong);
    padding: var(--space-5) var(--space-7);
    text-align: center;
}

.stat-label {
    color: var(--color-text-secondary);
    font-size: 0.84rem;
    font-weight: 700;
    margin-bottom: var(--space-1);
}

.stat-value {
    color: var(--color-surface-base);
    font-size: 1.75rem;
    font-weight: 800;
    line-height: 1.1;
    font-variant-numeric: tabular-nums;
}

.questions-container {
    display: flex;
    flex-direction: column;
    gap: var(--space-6);
    margin-bottom: var(--space-7);
}

fieldset.question-card {
    position: relative;
    border: 1px solid var(--color-border-strong);
    border-radius: var(--radius-lg);
    background-color: var(--color-surface-muted);
    padding: var(--space-7);
    box-shadow: var(--shadow-1);
    transition: border-color var(--motion-fast) ease, transform var(--motion-fast) ease;
}

fieldset.question-card:hover {
    border-color: var(--color-surface-raised);
}

legend {
    float: left;
    display: flex;
    align-items: flex-start;
    gap: var(--space-4);
    width: 100%;
    color: var(--color-text-secondary);
    font-size: var(--font-size-sm);
    font-weight: 800;
    line-height: 1.45;
    margin-bottom: var(--space-6);
    padding: 0;
}

.question-num {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 30px;
    height: 30px;
    flex-shrink: 0;
    margin-top: 1px;
    border-radius: var(--radius-sm);
    background-color: var(--color-surface-base);
    color: var(--color-surface-muted);
    font-size: 0.82rem;
    font-weight: 800;
    font-variant-numeric: tabular-nums;
}

.options-container {
    clear: both;
    display: flex;
    flex-direction: column;
    gap: var(--space-5);
    width: 100%;
}

.option-label {
    display: grid;
    grid-template-columns: auto 1fr auto;
    align-items: center;
    gap: var(--space-5);
    min-height: 48px;
    border: 1px solid var(--color-border-strong);
    border-radius: var(--radius-md);
    background: var(--color-surface-muted);
    color: var(--color-text-secondary);
    padding: var(--space-5) var(--space-6);
    cursor: pointer;
    transition: background-color var(--motion-instant) ease, border-color var(--motion-instant) ease, transform var(--motion-instant) ease;
}

.option-label:hover {
    border-color: var(--color-surface-raised);
    background-color: var(--color-surface-strong);
}

.option-label:active {
    transform: translateY(1px);
}

.option-label input[type="radio"] {
    width: 18px;
    height: 18px;
    accent-color: var(--color-surface-raised);
    cursor: pointer;
    flex-shrink: 0;
}

#examForm.is-submitted .option-label.correct-option {
    border-color: var(--color-success-border);
    background-color: var(--color-success-bg);
    color: var(--color-success-text);
    font-weight: 700;
}

#examForm.is-submitted .option-label.correct-option::after {
    content: "答對";
    color: var(--color-success-text);
    font-size: 0.82rem;
    font-weight: 800;
}

#examForm.is-submitted .option-label.incorrect-option {
    border-color: var(--color-error-border);
    background-color: var(--color-error-bg);
    color: var(--color-error-text);
    font-weight: 700;
}

#examForm.is-submitted .option-label.incorrect-option::after {
    content: "你的答案";
    color: var(--color-error-text);
    font-size: 0.82rem;
    font-weight: 800;
}

fieldset.question-card.unanswered-warning {
    border-color: var(--color-warning-border);
    background-color: var(--color-warning-bg);
}

fieldset.question-card.unanswered-warning::after {
    content: "未作答";
    position: absolute;
    top: var(--space-6);
    right: var(--space-6);
    color: var(--color-warning-text);
    font-size: 0.82rem;
    font-weight: 800;
}

#examForm.is-submitted fieldset.question-card.correct-card {
    border-color: var(--color-success-border);
}

#examForm.is-submitted fieldset.question-card.incorrect-card {
    border-color: var(--color-error-border);
}

code.inline-code {
    display: inline-block;
    margin: 0 2px;
    border: 1px solid var(--color-border-strong);
    border-radius: var(--radius-xs);
    background-color: var(--color-surface-strong);
    color: var(--color-text-secondary);
    padding: 2px var(--space-3);
    font-family: ui-monospace, SFMono-Regular, Consolas, Monaco, "Liberation Mono", monospace;
    font-size: 0.9em;
    white-space: nowrap;
}

.form-actions {
    display: flex;
    justify-content: flex-end;
    gap: var(--space-5);
    margin-top: var(--space-7);
}

@media (max-width: 760px) {
    body {
        padding-bottom: 214px;
    }

    main.app {
        padding: var(--space-6) var(--space-5) var(--space-8);
    }

    .hero,
    fieldset.question-card {
        padding: var(--space-6);
    }

    .hero {
        min-height: 330px;
        background:
            linear-gradient(90deg, rgba(0, 0, 0, 0.94) 0%, rgba(0, 0, 0, 0.7) 58%, rgba(0, 0, 0, 0.26) 100%),
            linear-gradient(180deg, rgba(0, 0, 0, 0.2) 0%, rgba(0, 0, 0, 0.72) 100%),
            url("hero-banner.png") center / cover no-repeat;
    }

    .brand-row {
        align-items: flex-start;
        flex-direction: column;
        gap: var(--space-4);
    }

    .sticky-status {
        grid-template-columns: 1fr;
        gap: var(--space-4);
        padding: var(--space-4) var(--space-5);
    }

    .status-left {
        align-items: stretch;
        flex-direction: column;
        gap: var(--space-4);
    }

    .progress-container {
        width: 100%;
    }

    .copyright {
        white-space: normal;
    }

    .footer-actions .btn,
    .form-actions .btn {
        width: 100%;
    }

    .form-actions {
        flex-direction: column;
    }
}

@media (max-width: 460px) {
    .option-label {
        grid-template-columns: auto 1fr;
    }

    #examForm.is-submitted .option-label.correct-option::after,
    #examForm.is-submitted .option-label.incorrect-option::after {
        grid-column: 2;
        justify-self: start;
    }
}

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.001ms !important;
        scroll-behavior: auto !important;
        transition-duration: 0.001ms !important;
    }
}