/* =============================================
   QUIZPREP — Global Stylesheet
   Stage 1: Landing Page
   ============================================= */

/* ── 1. Design Tokens ── */
:root {
    /* Brand colours */
    --color-primary: #1a5e3a;
    --color-primary-light: #2a8f57;
    --color-accent: #f5a623;
    --color-accent-dark: #d4891a;

    /* Surface colours */
    --color-bg: #ffffff;
    --color-bg-alt: #f5f8fc;
    --color-border: #d0dce8;

    /* Text colours */
    --color-text: #1a1a2e;
    --color-text-muted: #5a6a7a;
    --color-white: #ffffff;

    /* Typography */
    --font-base: "Segoe UI", system-ui, -apple-system, sans-serif;
    --fs-sm: 0.875rem;
    --fs-base: 1rem;
    --fs-lg: 1.125rem;
    --fs-xl: 1.5rem;
    --fs-2xl: 2rem;
    --fs-3xl: 2.75rem;

    /* Spacing scale */
    --space-xs: 0.5rem;
    --space-sm: 1rem;
    --space-md: 1.5rem;
    --space-lg: 2rem;
    --space-xl: 3rem;
    --space-2xl: 5rem;

    /* Misc */
    --container-max: 1100px;
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --shadow: 0 2px 16px rgba(26, 60, 94, 0.08);
    --transition: 0.2s ease;
}

/* =============================================
   DARK MODE — Deep Navy (GitHub style)
   ============================================= */

:root.dark {
  --color-primary:       #3fb950;
  --color-primary-light: #2ea043;
  --color-accent:        #f0883e;
  --color-accent-dark:   #db6d28;
  --color-bg:            #0d1117;
  --color-bg-alt:        #161b22;
  --color-border:        #30363d;
  --color-text:          #e6edf3;
  --color-text-muted:    #8b949e;
  --color-white:         #e6edf3;
  --shadow:              0 2px 16px rgba(0, 0, 0, 0.6);
}

:root.dark .nav {
  background: #161b22;
  border-bottom: 1px solid #30363d;
}

:root.dark .btn--outline {
  color: #e6edf3;
  border-color: #30363d;
}
:root.dark .btn--outline:hover {
  background: #21262d;
  color: #e6edf3;
  border-color: #8b949e;
}

:root.dark .btn--outline-dark {
  color: #e6edf3;
  border-color: #30363d;
}
:root.dark .btn--outline-dark:hover {
  background: #21262d;
  border-color: #8b949e;
}

:root.dark .btn--primary {
  background: #238636;
  border-color: #238636;
  color: #ffffff;
}
:root.dark .btn--primary:hover {
  background: #2ea043;
  border-color: #2ea043;
}

:root.dark .how__card,
:root.dark .feature__card,
:root.dark .subject-card,
:root.dark .quiz-card,
:root.dark .hist-stat-card,
:root.dark .modal {
  background: #161b22;
  border-color: #30363d;
}

:root.dark .how__card:hover,
:root.dark .feature__card:hover,
:root.dark .subject-card:hover {
  border-color: #3fb950;
  box-shadow: 0 0 0 1px #3fb950;
}

:root.dark .hero,
:root.dark .qs-header,
:root.dark .score-hero,
:root.dark .history-header {
  background: linear-gradient(135deg, #161b22 0%, #0d1117 100%);
  border-bottom: 1px solid #30363d;
}

:root.dark .how { background: #0d1117; }
:root.dark .how__num { background: #238636; }

:root.dark .quiz-topbar {
  background: #161b22;
  border-bottom: 1px solid #30363d;
}

:root.dark .timer {
  background: rgba(255,255,255,0.06);
  border: 1px solid #30363d;
}
:root.dark .timer.danger {
  background: rgba(248,81,73,0.15);
  border-color: #f85149;
}
:root.dark .timer.danger .timer__display { color: #f85149; }
:root.dark .quiz-progress { background: #21262d; }
:root.dark .quiz-main { background: #0d1117; }

:root.dark .option-btn {
  background: #161b22;
  border-color: #30363d;
  color: #e6edf3;
}
:root.dark .option-btn:hover {
  background: #21262d;
  border-color: #8b949e;
}
:root.dark .option-btn.selected {
  background: rgba(63,185,80,0.1);
  border-color: #3fb950;
  color: #3fb950;
}
:root.dark .option-btn.selected .option-label {
  background: #238636;
  border-color: #238636;
  color: #ffffff;
}
:root.dark .option-label {
  border-color: #30363d;
  color: #8b949e;
}

:root.dark .form-input {
  background: #0d1117;
  border-color: #30363d;
  color: #e6edf3;
}
:root.dark .form-input:focus {
  border-color: #3fb950;
  box-shadow: 0 0 0 3px rgba(63,185,80,0.12);
}
:root.dark .form-input::placeholder { color: #484f58; }

:root.dark .history-select {
  background: #161b22;
  border-color: #30363d;
  color: #e6edf3;
}
:root.dark .history-select:focus { border-color: #3fb950; }

:root.dark .history-table-wrap { border-color: #30363d; }
:root.dark .history-table thead tr { background: #161b22; }
:root.dark .history-table th {
  color: #8b949e;
  border-bottom: 1px solid #30363d;
}
:root.dark .history-table tbody tr { border-color: #21262d; }
:root.dark .history-table tbody tr:hover { background: #161b22; }
:root.dark .history-table td { color: #e6edf3; }

:root.dark .stats-bar,
:root.dark .hist-stats {
  background: #161b22;
  border-color: #30363d;
}
:root.dark .stat__value,
:root.dark .hist-stat__value { color: #3fb950; }

:root.dark .review-card {
  background: #161b22;
  border-color: #30363d;
}
:root.dark .review-card__header { background: #0d1117; }
:root.dark .review-card__header:hover { background: #161b22; }
:root.dark .review-card__question { color: #e6edf3; }
:root.dark .review-option {
  background: #0d1117;
  border-color: #30363d;
  color: #e6edf3;
}
:root.dark .review-option.is-correct {
  background: rgba(63,185,80,0.1);
  border-color: #3fb950;
  color: #3fb950;
}
:root.dark .review-option.user-wrong {
  background: rgba(248,81,73,0.1);
  border-color: #f85149;
  color: #f85149;
}
:root.dark .review-badge.correct {
  background: rgba(63,185,80,0.15);
  color: #3fb950;
}
:root.dark .review-badge.wrong {
  background: rgba(248,81,73,0.15);
  color: #f85149;
}
:root.dark .review-badge.skipped {
  background: rgba(210,153,34,0.15);
  color: #d29922;
}

:root.dark .score-ring__track { stroke: #21262d; }
:root.dark .score-ring__raw { color: #8b949e; }

:root.dark .modal-overlay { background: rgba(0,0,0,0.75); }
:root.dark .modal {
  background: #161b22;
  border: 1px solid #30363d;
}
:root.dark .modal__title { color: #e6edf3; }

:root.dark .filter-btn,
:root.dark .review-filter {
  border-color: #30363d;
  color: #8b949e;
  background: transparent;
}
:root.dark .filter-btn:hover,
:root.dark .review-filter:hover {
  border-color: #8b949e;
  color: #e6edf3;
}
:root.dark .filter-btn.active,
:root.dark .review-filter.active {
  background: #238636;
  border-color: #238636;
  color: #ffffff;
}

:root.dark .footer {
  background: #161b22;
  border-top: 1px solid #30363d;
}

:root.dark .section__title { color: #e6edf3; }

:root.dark .subject-card__name,
:root.dark .how__heading,
:root.dark .feature__title { color: #e6edf3; }

:root.dark .nav__logo { color: #e6edf3; }
:root.dark .nav__logo span { color: #f0883e; }

.theme-toggle {
  background: none;
  border: none;
  cursor: pointer;
  font-size: 1.1rem;
  padding: 4px 8px;
  border-radius: var(--radius-sm);
  transition: background var(--transition);
  line-height: 1;
  color: var(--color-white);
}
.theme-toggle:hover { background: rgba(255,255,255,0.1); }

:root.dark ::-webkit-scrollbar-track { background: #0d1117; }
:root.dark ::-webkit-scrollbar-thumb { background: #30363d; }
:root.dark ::-webkit-scrollbar-thumb:hover { background: #3fb950; }

:root.dark ::selection {
  background: #238636;
  color: #ffffff;
}

:root.dark .btn--danger {
  color: #f85149;
  border-color: rgba(248,81,73,0.3);
}
:root.dark .btn--danger:hover {
  background: rgba(248,81,73,0.1);
  border-color: #f85149;
}

:root.dark .history-empty__title,
:root.dark .notfound__title { color: #e6edf3; }

:root.dark #quitBtn {
  border-color: #30363d;
  color: #e6edf3;
}
:root.dark #quitBtn:hover { background: #21262d; }

/* ── 2. Reset ── */
*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-base);
    font-size: var(--fs-base);
    color: var(--color-text);
    background: var(--color-bg);
    line-height: 1.7;
}

a {
    text-decoration: none;
    color: inherit;
}
img {
    max-width: 100%;
    display: block;
}

/* ── 3. Layout Utility ── */
.container {
    width: 90%;
    max-width: var(--container-max);
    margin-inline: auto;
}

/* ── 4. Buttons ── */
.btn {
    display: inline-block;
    padding: 0.75rem 1.75rem;
    border-radius: var(--radius-md);
    font-size: var(--fs-base);
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition);
    border: 2px solid transparent;
}

.btn--primary {
    background: var(--color-accent);
    color: var(--color-primary);
    border-color: var(--color-accent);
}
.btn--primary:hover {
    background: var(--color-accent-dark);
    border-color: var(--color-accent-dark);
    transform: translateY(-2px);
}

.btn--outline {
    background: transparent;
    color: var(--color-white);
    border-color: var(--color-white);
}
.btn--outline:hover {
    background: var(--color-white);
    color: var(--color-primary);
}

/* ── 5. Navigation ── */
.nav {
    background: var(--color-primary);
    padding: var(--space-sm) 0;
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow);
}

.nav__inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.nav__logo {
    font-size: var(--fs-xl);
    font-weight: 800;
    color: var(--color-white);
    letter-spacing: -0.5px;
}
.nav__logo span {
    color: var(--color-accent);
}

/* ── 6. Hero ── */
.hero {
    background: linear-gradient(
        135deg,
        var(--color-primary) 0%,
        var(--color-primary-light) 100%
    );
    color: var(--color-white);
    padding: var(--space-2xl) 0;
    text-align: center;
}

.hero__inner {
    max-width: 700px;
}

.hero__title {
    font-size: var(--fs-3xl);
    font-weight: 800;
    line-height: 1.2;
    margin-bottom: var(--space-md);
}

.hero__sub {
    font-size: var(--fs-lg);
    color: rgba(255, 255, 255, 0.85);
    max-width: 560px;
    margin-inline: auto;
    margin-bottom: var(--space-lg);
}

/* ── 7. Section Base ── */
.section {
    padding: var(--space-2xl) 0;
}

.section__title {
    font-size: var(--fs-2xl);
    font-weight: 700;
    color: var(--color-primary);
    text-align: center;
    margin-bottom: var(--space-xl);
}

/* ── 8. How It Works ── */
.how {
    background: var(--color-bg-alt);
}

.how__grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: var(--space-md);
}

.how__card {
    background: var(--color-bg);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    text-align: center;
    box-shadow: var(--shadow);
    transition: transform var(--transition);
}
.how__card:hover {
    transform: translateY(-4px);
}

.how__num {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: var(--color-primary);
    color: var(--color-white);
    font-size: var(--fs-xl);
    font-weight: 700;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto var(--space-sm);
}

.how__heading {
    font-size: var(--fs-lg);
    font-weight: 600;
    color: var(--color-primary);
    margin-bottom: var(--space-xs);
}
.how__text {
    color: var(--color-text-muted);
    font-size: var(--fs-sm);
}

/* ── 9. Features ── */
.features__grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
    gap: var(--space-md);
}

.feature__card {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    transition: all var(--transition);
}
.feature__card:hover {
    border-color: var(--color-primary);
    box-shadow: var(--shadow);
    transform: translateY(-2px);
}

.feature__icon {
    font-size: 2rem;
    margin-bottom: var(--space-sm);
}

.feature__title {
    font-size: var(--fs-lg);
    font-weight: 600;
    color: var(--color-primary);
    margin-bottom: var(--space-xs);
}
.feature__text {
    color: var(--color-text-muted);
    font-size: var(--fs-sm);
}

/* ── 10. Footer ── */
.footer {
    background: var(--color-primary);
    color: var(--color-white);
    padding: var(--space-lg) 0;
}

.footer__inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: var(--space-sm);
}
.footer__copy {
    color: rgba(255, 255, 255, 0.7);
    font-size: var(--fs-sm);
}

/* ── 11. Responsive ── */
@media (max-width: 600px) {
    .hero__title {
        font-size: var(--fs-2xl);
    }
    .hero__sub {
        font-size: var(--fs-base);
    }
    .section__title {
        font-size: var(--fs-xl);
    }
    .footer__inner {
        flex-direction: column;
        text-align: center;
    }
}

/* =============================================
   STAGE 9 — Final Polish
   ============================================= */

/* ── Smooth page load ── */
body {
    animation: fadeIn 0.2s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(4px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ── Focus rings — keyboard navigation ── */
*:focus-visible {
    outline: 3px solid var(--color-accent);
    outline-offset: 3px;
    border-radius: var(--radius-sm);
}

/* ── Button press effect ── */
.btn:active {
    transform: scale(0.97);
}

/* ── Text selection colour ── */
::selection {
    background: var(--color-primary);
    color: var(--color-white);
}

:root.dark ::selection {
    background: var(--color-accent);
    color: #0f1117;
}

/* ── Custom scrollbar ── */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}

::-webkit-scrollbar-track {
    background: var(--color-bg-alt);
}

::-webkit-scrollbar-thumb {
    background: var(--color-border);
    border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--color-primary);
}

/* ── Prevent nav height shift ── */
.nav__inner {
    min-height: 52px;
}

/* ── Images never overflow ── */
img,
svg {
    display: block;
    max-width: 100%;
}