:root {
    color-scheme: light;
    --bg: #ffffff;
    --surface: #ffffff;
    --surface-soft: #fafafa;
    --ink: #0f0f10;
    --ink-soft: #6b6b70;
    --line: #d4d4d4;
    --line-strong: #c0c0c0;
    --accent: #2f4ad0;
    --accent-soft: #eef1fc;
    --ok: #1f9d55;
    --ok-soft: #e7f6ec;
    --bad: #c53030;
    --bad-soft: #fdecec;
    --space: #080914;
    --space-soft: #11152b;
    --star: #f5f5f7;
    --sun: #d97706;
    --sun-soft: #fff4cc;
    --ray: #f6c945;
    --planet: #3d6fd8;
    --dust: #b79b69;
    --shadow-card: 0 8px 24px -12px rgba(15, 15, 16, 0.18);
    --shadow-focus: 0 0 0 4px rgba(15, 15, 16, 0.06);
    --shadow-toplink: 0 4px 14px -6px rgba(15, 15, 16, 0.12);
}

[data-theme="dark"] {
    color-scheme: dark;
    --bg: #0c0c0e;
    --surface: #141418;
    --surface-soft: #1c1c21;
    --ink: #f5f5f7;
    --ink-soft: #9b9ba3;
    --line: #2e2e35;
    --line-strong: #44444c;
    --accent: #7c8fff;
    --accent-soft: #1c2244;
    --ok: #4ade80;
    --ok-soft: #102a1a;
    --bad: #f87171;
    --bad-soft: #2c1414;
    --space: #05060d;
    --space-soft: #101427;
    --star: #f5f5f7;
    --sun: #f59e0b;
    --sun-soft: #422b0b;
    --ray: #facc15;
    --planet: #7c8fff;
    --dust: #c0a36f;
    --shadow-card: 0 8px 24px -8px rgba(0, 0, 0, 0.6);
    --shadow-focus: 0 0 0 4px rgba(124, 143, 255, 0.18);
    --shadow-toplink: 0 4px 14px -6px rgba(0, 0, 0, 0.6);
}

* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Inter", "Helvetica Neue", Helvetica, Arial, sans-serif;
    font-size: 16px;
    line-height: 1.55;
    letter-spacing: -0.005em;
    -webkit-font-smoothing: antialiased;
    background: var(--bg);
    color: var(--ink);
}

a {
    color: inherit;
    text-decoration: none;
}

button {
    font: inherit;
}

.skip-link {
    position: absolute;
    top: -100%;
    left: 16px;
    padding: 12px 24px;
    background: var(--accent);
    color: var(--bg);
    border-radius: 0 0 12px 12px;
    font-weight: 600;
    z-index: 100;
}

.skip-link:focus {
    top: 0;
}

.page-shell {
    width: min(1120px, calc(100% - 40px));
    margin: 0 auto;
    padding: 20px 0 80px;
}

.nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 0;
    border-bottom: 1px solid var(--line);
    margin-bottom: 32px;
}

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

.brand-mark {
    display: grid;
    place-items: center;
    width: 28px;
    height: 28px;
    background: var(--ink);
    color: var(--bg);
    border-radius: 6px;
    font-size: 14px;
}

.brand-name {
    font-weight: 600;
    font-size: 0.95rem;
    letter-spacing: -0.01em;
}

.brand-dot {
    color: var(--ink-soft);
}

.nav-actions {
    display: flex;
    align-items: center;
    gap: 12px;
}

.nav-tag {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    font-size: 0.75rem;
    color: var(--ink-soft);
    padding: 6px 12px;
    border: 1px solid var(--line);
    border-radius: 999px;
}

.theme-toggle {
    display: inline-grid;
    place-items: center;
    width: 38px;
    height: 38px;
    border: 1px solid var(--line);
    border-radius: 50%;
    background: var(--surface-soft);
    color: var(--ink);
    cursor: pointer;
    font-size: 14px;
    padding: 0;
}

.theme-toggle:hover,
.theme-toggle:focus-visible {
    background: var(--accent-soft);
    border-color: var(--accent);
    color: var(--accent);
    outline: 0;
}

.theme-toggle-icon { display: none; }
[data-theme="dark"] .theme-toggle-icon-light { display: inline-block; }
:root:not([data-theme="dark"]) .theme-toggle-icon-dark { display: inline-block; }

.breadcrumb {
    margin-bottom: 24px;
}

.breadcrumb a {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    font-size: 0.875rem;
    color: var(--ink-soft);
    padding: 8px 16px;
    border: 1px solid var(--line);
    border-radius: 999px;
    transition: color 0.2s, border-color 0.2s, background 0.2s;
}

.breadcrumb a:hover,
.breadcrumb a:focus-visible {
    color: var(--accent);
    border-color: var(--accent);
    background: var(--accent-soft);
    outline: 0;
}

.hero {
    max-width: 880px;
    padding-bottom: clamp(44px, 7vw, 72px);
}

.eyebrow {
    font-size: 0.78rem;
    text-transform: uppercase;
    letter-spacing: 0.18em;
    font-weight: 600;
    color: var(--accent);
    margin: 0 0 12px;
}

.hero h1 {
    font-size: clamp(2.2rem, 7vw, 5rem);
    font-weight: 600;
    letter-spacing: -0.035em;
    line-height: 1.05;
    margin: 0 0 20px;
}

.hero p:not(.eyebrow),
.mission-head p,
.compare-card p {
    color: var(--ink-soft);
    margin: 0;
}

.hero p:not(.eyebrow) {
    font-size: clamp(1.05rem, 2vw, 1.2rem);
    max-width: 680px;
}

.mission-grid {
    display: grid;
    grid-template-columns: minmax(0, 1.35fr) minmax(280px, 0.65fr);
    gap: 16px;
    align-items: stretch;
    padding-top: 32px;
    border-top: 1px solid var(--line);
}

.mission-card,
.control-card,
.compare-card,
.practice-card {
    border: 1px solid var(--line);
    border-radius: 18px;
    background: var(--surface);
    padding: 22px;
}

.mission-head {
    margin-bottom: 22px;
}

.mission-head h2,
.control-card h2,
.compare-card h2,
.practice-question h2,
.summary-card h2 {
    font-size: clamp(1.5rem, 2.5vw, 1.85rem);
    font-weight: 600;
    letter-spacing: -0.025em;
    line-height: 1.1;
    margin: 0 0 10px;
}

.control-card h2 {
    font-size: clamp(1.3rem, 2vw, 1.6rem);
}

.control-card p:not(.eyebrow) {
    color: var(--ink-soft);
    margin: 0 0 16px;
}

.space-stage {
    position: relative;
    min-height: 420px;
    overflow: hidden;
    border-radius: 16px;
    background: var(--space);
    border: 1px solid var(--line);
}

#light-canvas {
    display: block;
    width: 100%;
    height: 100%;
    min-height: 420px;
}

.scene-hint {
    position: absolute;
    left: 50%;
    bottom: 16px;
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 10px;
    width: calc(100% - 32px);
    transform: translateX(-50%);
    color: var(--star);
    font-size: 0.8rem;
    pointer-events: none;
}

.scene-hint span {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 8px 12px;
    border: 1px solid var(--line-strong);
    border-radius: 999px;
    background: var(--space-soft);
}

.planet-labels {
    position: absolute;
    inset: 0;
    pointer-events: none;
}

.planet-label {
    position: absolute;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    min-width: max-content;
    padding: 0;
    color: var(--star);
    font-size: 0.9rem;
    font-weight: 600;
    text-shadow: 0 1px 3px var(--space);
    transform: translate(-50%, -50%);
}

.planet-label span {
    color: var(--star);
    font-weight: 500;
}

.planet-label.is-hidden {
    display: none;
}

.fullscreen-button,
.scene-play-button {
    position: absolute;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    min-height: 48px;
    padding: 10px 14px;
    border: 1px solid var(--line-strong);
    border-radius: 999px;
    background: var(--space-soft);
    color: var(--star);
    font: inherit;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    z-index: 3;
}

.fullscreen-button {
    top: 16px;
    right: 16px;
}

.scene-play-button {
    top: 16px;
    left: 16px;
}

.fullscreen-button:hover,
.fullscreen-button:focus-visible,
.scene-play-button:hover,
.scene-play-button:focus-visible {
    border-color: var(--ray);
    color: var(--ray);
    outline: 0;
}

.space-stage:fullscreen {
    border-radius: 0;
    border: 0;
    width: 100vw;
    height: 100vh;
}

.space-stage:-webkit-full-screen {
    border-radius: 0;
    border: 0;
    width: 100vw;
    height: 100vh;
}

.space-stage:fullscreen #light-canvas,
.space-stage:-webkit-full-screen #light-canvas {
    min-height: 100vh;
}

.timer-panel {
    display: grid;
    gap: 4px;
    margin-top: 18px;
    padding: 16px;
    border: 1px solid var(--line);
    border-radius: 14px;
    background: var(--surface-soft);
}

.timer-label,
.timer-panel span:last-child {
    color: var(--ink-soft);
    font-size: 0.9rem;
}

.timer-panel strong {
    font-size: clamp(1.6rem, 4vw, 2.8rem);
    letter-spacing: -0.035em;
    line-height: 1.05;
}

.answer-options {
    display: grid;
    gap: 10px;
}

.answer-button,
.restart-button {
    min-height: 56px;
    border: 1px solid var(--line);
    border-radius: 12px;
    background: var(--surface);
    color: var(--ink);
    font-weight: 600;
    font-size: 1rem;
    cursor: pointer;
    transition: background 0.2s, border-color 0.2s, color 0.2s, transform 0.2s;
}

.answer-button:hover,
.answer-button:focus-visible,
.restart-button:hover,
.restart-button:focus-visible {
    background: var(--accent-soft);
    border-color: var(--accent);
    color: var(--accent);
    outline: 0;
}

.play-button,
.next-button {
    background: var(--ink);
    border-color: var(--ink);
    color: var(--bg);
}

.time-list {
    list-style: none;
    display: grid;
    gap: 10px;
    padding: 0;
    margin: 18px 0 0;
}

.time-list li {
    display: flex;
    justify-content: space-between;
    gap: 12px;
    padding: 10px 0;
    border-top: 1px solid var(--line);
    color: var(--ink-soft);
    font-size: 0.9rem;
}

.time-list strong {
    color: var(--ink);
}

.play-button,
.next-button,
.restart-button {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 18px;
}

.compare-card,
.practice-card {
    margin-top: 16px;
}

.compare-card {
    display: grid;
    grid-template-columns: minmax(240px, 0.65fr) minmax(0, 1fr);
    gap: 20px;
    align-items: center;
}

.compare-bars {
    display: grid;
    gap: 12px;
}

.compare-row {
    display: grid;
    gap: 6px;
}

.compare-label {
    display: flex;
    justify-content: space-between;
    gap: 12px;
    color: var(--ink-soft);
    font-size: 0.9rem;
}

.compare-track {
    height: 14px;
    border-radius: 999px;
    background: var(--surface-soft);
    border: 1px solid var(--line);
    overflow: hidden;
}

.compare-fill {
    display: block;
    height: 100%;
    width: 0%;
    background: var(--accent);
    border-radius: 999px;
}

.practice-status {
    display: flex;
    flex-wrap: wrap;
    justify-content: space-between;
    gap: 12px;
    color: var(--ink-soft);
    font-size: 0.9rem;
    margin-bottom: 18px;
}

.practice-status p,
.feedback,
.summary-card p {
    margin: 0;
}

.practice-question {
    margin-bottom: 18px;
}

.answer-options {
    grid-template-columns: repeat(2, minmax(0, 1fr));
}

.answer-button {
    padding: 12px 14px;
}

.answer-button.is-correct {
    background: var(--ok-soft);
    border-color: var(--ok);
    color: var(--ok);
}

.answer-button.is-wrong {
    background: var(--bad-soft);
    border-color: var(--bad);
    color: var(--bad);
}

.answer-button:disabled {
    cursor: default;
}

.feedback {
    margin-top: 16px;
    color: var(--ink-soft);
}

.next-button {
    margin-top: 16px;
}

.summary-card[hidden],
.next-button[hidden] {
    display: none;
}

.summary-list {
    margin: 18px 0;
    padding-left: 24px;
    color: var(--ink-soft);
}

.summary-list li + li {
    margin-top: 8px;
}

.foot {
    display: flex;
    justify-content: space-between;
    padding: 24px 0;
    margin-top: 64px;
    border-top: 1px solid var(--line);
    font-size: 0.875rem;
    color: var(--ink-soft);
}

@media (prefers-reduced-motion: reduce) {
    .scene-hint {
        display: none;
    }
}

@media (max-width: 860px) {
    .mission-grid,
    .compare-card {
        grid-template-columns: 1fr;
    }

    .space-stage {
        min-height: 360px;
    }

    #light-canvas { min-height: 360px; }
}

@media (max-width: 760px) {
    .page-shell {
        width: min(100% - 28px, 1120px);
    }

    .nav,
    .foot,
    .practice-status {
        align-items: flex-start;
        flex-direction: column;
    }

    .nav-actions {
        width: 100%;
        justify-content: space-between;
    }

    .space-stage {
        min-height: 300px;
    }

    #light-canvas { min-height: 300px; }

    .fullscreen-button,
    .scene-play-button {
        max-width: calc(50% - 22px);
        font-size: 0.75rem;
        padding: 8px 10px;
    }

    .answer-options {
        grid-template-columns: 1fr;
    }

    .answer-button,
    .restart-button,
    .play-button,
    .next-button {
        width: 100%;
    }
}