:root {
    --color-background: #f5f7fb;
    --color-surface: #ffffff;
    --color-surface-soft: #eef3f8;
    --color-text: #172033;
    --color-text-soft: #596579;
    --color-primary: #245f73;
    --color-primary-strong: #174858;
    --color-primary-soft: #dcebef;
    --color-background-soft: #eef3f8;
    --color-background-mute: #dcebef;
    --color-white-soft: #ffffff;
    --color-black-soft: #172033;
    --color-success: #1f7a4d;
    --color-success-soft: #e5f4eb;
    --color-danger: #b42318;
    --color-danger-soft: #fdebea;
    --color-warning: #93640c;
    --color-warning-soft: #fff4db;
    --color-border: #d8e0ea;
    --color-border-soft: #e8edf3;
    --shadow-sm: 0 1px 2px rgba(23, 32, 51, 0.06);
    --shadow-md: 0 10px 24px rgba(23, 32, 51, 0.08);
    --radius: 8px;
}

body[theme-mode="dark"] {
    --color-background: #101923;
    --color-surface: #172331;
    --color-surface-soft: #223244;
    --color-text: #f2f5f8;
    --color-text-soft: #b9c4d0;
    --color-primary: #5bb3c8;
    --color-primary-strong: #8fd5e4;
    --color-primary-soft: #203b45;
    --color-background-soft: #223244;
    --color-background-mute: #203b45;
    --color-white-soft: #172331;
    --color-black-soft: #f2f5f8;
    --color-border: #34465a;
    --color-border-soft: #263646;
}

* {
    box-sizing: border-box;
}

html {
    -webkit-text-size-adjust: 100%;
}

body {
    margin: 0;
    min-height: 100vh;
    background: var(--color-background);
    color: var(--color-text);
    font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
    font-size: 15px;
    line-height: 1.55;
}

a {
    color: inherit;
}

button,
input,
select,
textarea {
    font: inherit;
}

.page {
    width: min(1120px, 100%);
    margin: 0 auto;
    padding: 18px;
}

.page-wide {
    width: min(1320px, 100%);
}

.topbar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    min-height: 56px;
    padding: 4px 0 16px;
}

.brand {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 22px;
    font-weight: 800;
    color: var(--color-text);
    letter-spacing: 0;
}

.top-actions {
    gap: 8px;
    justify-content: flex-end;
}

.grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 12px;
}

.stack {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.card {
    background: var(--color-surface);
    border: 1px solid var(--color-border-soft);
    border-radius: var(--radius);
    padding: 16px;
    box-shadow: var(--shadow-sm);
}

.card h3 {
    margin: 0;
    font-size: 18px;
}

.card p {
    margin: 0;
    color: var(--color-text-soft);
}

.exam-shell {
    max-width: 820px;
    margin-inline: auto;
}

.status-card {
    position: sticky;
    top: 0;
    z-index: 5;
}

.btn {
    appearance: none;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    min-height: 42px;
    border: 1px solid var(--color-primary);
    background: var(--color-primary);
    color: #fff;
    padding: 10px 14px;
    border-radius: var(--radius);
    font-weight: 700;
    font-size: 14px;
    text-decoration: none;
    cursor: pointer;
    box-shadow: var(--shadow-sm);
    transition: background 0.12s ease, border-color 0.12s ease, transform 0.12s ease;
}

.btn:hover {
    background: var(--color-primary-strong);
    border-color: var(--color-primary-strong);
    transform: translateY(-1px);
}

.btn:active {
    transform: translateY(0);
}

.btn:disabled {
    opacity: 0.55;
    cursor: not-allowed;
    transform: none;
}

.btn.secondary {
    background: var(--color-surface-soft);
    border-color: var(--color-border);
    color: var(--color-text);
    box-shadow: none;
}

.btn.secondary:hover {
    background: #e2eaf2;
    border-color: #c9d5e2;
}

.btn.ghost {
    background: transparent;
    border-color: var(--color-border);
    color: var(--color-primary-strong);
    box-shadow: none;
}

.btn.ghost:hover {
    background: var(--color-primary-soft);
    border-color: var(--color-primary);
}

.btn.submit-small {
    width: auto;
}

.btn.submit-accent {
    width: 100%;
    min-height: 48px;
    background: var(--color-success);
    border-color: var(--color-success);
    color: #fff;
}

.btn.submit-accent:hover {
    background: #17643f;
    border-color: #17643f;
}

.input {
    width: 100%;
    min-height: 44px;
    padding: 10px 12px;
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    background: var(--color-surface);
    color: var(--color-text);
    outline: none;
}

.input:focus {
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(36, 95, 115, 0.14);
}

textarea.input {
    resize: vertical;
}

.pill,
.tag,
.chip {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    border-radius: var(--radius);
    border: 1px solid transparent;
    line-height: 1.25;
}

.pill {
    min-height: 30px;
    padding: 6px 10px;
    background: var(--color-primary-soft);
    color: var(--color-primary-strong);
    font-size: 13px;
    font-weight: 700;
}

.tag {
    min-height: 28px;
    padding: 5px 9px;
    background: var(--color-surface-soft);
    color: var(--color-text-soft);
    font-size: 13px;
    font-weight: 650;
}

.tag.accent {
    background: var(--color-primary);
    color: #fff;
}

.tag.mild {
    background: var(--color-surface-soft);
    color: var(--color-text-soft);
}

.chips {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.chip {
    min-height: 32px;
    padding: 7px 10px;
    background: var(--color-surface-soft);
    border-color: var(--color-border-soft);
    color: var(--color-text-soft);
    font-size: 13px;
    font-weight: 700;
    cursor: pointer;
}

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

.question-card {
    padding: 16px;
    border-radius: var(--radius);
    background: var(--color-surface);
    border: 1px solid var(--color-border);
}

.question-stem {
    margin: 10px 0 2px;
    font-size: 18px;
    font-weight: 750;
    line-height: 1.55;
}

.options {
    display: flex;
    flex-direction: column;
    gap: 10px;
    margin-top: 14px;
}

.option {
    display: grid;
    grid-template-columns: 22px 1fr;
    align-items: start;
    gap: 10px;
    min-height: 46px;
    padding: 12px;
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    background: #fbfcfe;
    cursor: pointer;
}

.option:hover {
    border-color: var(--color-primary);
    background: #f3f8fa;
}

.option input {
    width: 18px;
    height: 18px;
    margin: 2px 0 0;
    accent-color: var(--color-primary);
}

.progress {
    flex: 1;
    min-width: 80px;
    height: 10px;
    overflow: hidden;
    background: var(--color-surface-soft);
    border-radius: 999px;
}

.progress-bar {
    height: 100%;
    width: 0;
    background: var(--color-primary);
    transition: width 0.2s ease;
}

.hint {
    background: var(--color-surface-soft);
    border: 1px solid var(--color-border-soft);
    border-radius: var(--radius);
    padding: 10px 12px;
    color: var(--color-text-soft);
    font-size: 13px;
}

.success {
    color: var(--color-success);
}

.hint.success,
.card.success {
    background: var(--color-success-soft);
    border-color: #b9dfc7;
}

.danger {
    color: var(--color-danger);
}

.hint.danger,
.card.danger {
    background: var(--color-danger-soft);
    border-color: #fac5c1;
}

.warning {
    color: var(--color-warning);
}

.hint.warning,
.card.warning {
    background: var(--color-warning-soft);
    border-color: #efd08a;
}

.small {
    font-size: 12px;
    color: var(--color-text-soft);
}

.emphasis {
    font-weight: 800;
}

.divider {
    width: 100%;
    height: 1px;
    margin: 10px 0;
    background: var(--color-border-soft);
}

.flex {
    display: flex;
    gap: 10px;
    align-items: center;
    flex-wrap: wrap;
}

.flex.between {
    justify-content: space-between;
}

.action-card {
    display: grid;
    grid-template-columns: minmax(140px, 1fr) minmax(180px, 1.4fr);
    gap: 10px;
    align-items: stretch;
    background: transparent;
    border: 0;
    box-shadow: none;
    padding: 0;
}

.nav-row {
    align-items: stretch;
}

.timer {
    font-weight: 800;
    color: var(--color-primary-strong);
}

.panel,
.field-block {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: 12px;
}

.card-error {
    border-color: #f0aaa4;
    background: #fff8f7;
}

.card-correct {
    border-color: #a7d7b8;
    background: #f4fbf6;
}

.modal-backdrop {
    position: fixed;
    inset: 0;
    z-index: 20;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 16px;
    background: rgba(15, 24, 38, 0.45);
}

.modal {
    width: min(760px, 100%);
    max-height: min(760px, calc(100vh - 32px));
    overflow: auto;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: 16px;
    box-shadow: var(--shadow-md);
}

.jump-body {
    margin-top: 12px;
}

.jump-groups {
    display: grid;
    gap: 10px;
}

.jump-grid {
    grid-template-columns: repeat(auto-fit, minmax(52px, 1fr));
    gap: 8px;
    margin-top: 8px;
}

.two-col-mobile {
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 10px;
}

.leaderboard,
.lb-grid {
    display: grid;
    gap: 12px;
}

.lb-grid {
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
}

.lb-row,
.lb-card {
    background: var(--color-surface);
    border: 1px solid var(--color-border-soft);
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
}

.lb-row {
    display: grid;
    grid-template-columns: 52px 1fr 72px 96px;
    align-items: center;
    gap: 10px;
    padding: 10px;
}

.lb-card {
    display: grid;
    gap: 10px;
    padding: 14px;
}

.lb-card.rank-1 {
    border-color: #e1b949;
}

.lb-card.rank-2 {
    border-color: #aeb8c5;
}

.lb-card.rank-3 {
    border-color: #c88454;
}

.badge {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-width: 34px;
    min-height: 32px;
    padding: 6px 10px;
    border-radius: var(--radius);
    background: var(--color-primary);
    color: #fff;
    font-weight: 800;
}

.lb-card.rank-1 .badge {
    background: #e1b949;
    color: #1d2430;
}

.lb-card.rank-2 .badge {
    background: #c7d0dc;
    color: #1d2430;
}

.lb-card.rank-3 .badge {
    background: #c88454;
    color: #fff;
}

.lb-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}

.lb-score {
    font-weight: 800;
}

.lb-user {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 10px;
}

.user-name {
    font-size: 18px;
    font-weight: 800;
    color: var(--color-text);
}

.chip.dept {
    border-color: currentColor;
    font-weight: 700;
}

.list {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.list-row {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: 10px;
    padding: 10px;
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    background: var(--color-surface);
}

.floating-action {
    position: fixed;
    right: 16px;
    bottom: 16px;
    z-index: 10;
}

@media (max-width: 820px) {
    .page {
        padding: 12px;
    }

    .topbar {
        align-items: flex-start;
        flex-direction: column;
        padding-bottom: 12px;
    }

    .brand {
        font-size: 20px;
    }

    .top-actions,
    .top-actions .btn,
    .top-actions .pill {
        width: 100%;
    }

    .top-actions {
        display: grid;
        grid-template-columns: 1fr 1fr;
    }

    .top-actions .pill {
        grid-column: 1 / -1;
        justify-content: center;
    }

    .card {
        padding: 14px;
    }

    .question-stem {
        font-size: 17px;
    }

    .action-card {
        grid-template-columns: 1fr;
    }

    .nav-row .btn,
    .flex.between .btn {
        flex: 1 1 140px;
    }

    .lb-row {
        grid-template-columns: 40px 1fr;
    }
}

@media (max-width: 520px) {
    body {
        font-size: 14px;
    }

    .page {
        padding: 10px;
    }

    .top-actions {
        grid-template-columns: 1fr;
    }

    .grid,
    .lb-grid,
    .two-col-mobile {
        grid-template-columns: 1fr;
    }

    .card,
    .question-card {
        padding: 12px;
    }

    .option {
        padding: 11px;
    }

    .flex.between {
        align-items: stretch;
    }

    .progress {
        flex-basis: 100%;
        order: 3;
    }

    .modal {
        max-height: calc(100vh - 20px);
        padding: 12px;
    }
}