: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;
    --shadow-card: 0 8px 24px -12px rgba(15, 15, 16, 0.18);
    --shadow-focus: 0 0 0 4px rgba(15, 15, 16, 0.06);
    --hero-bg: #f0fbe6;
    --highlight-bg: #f5f3ff;
    --hc-astro: #d4c6fd;
    --hc-physics: #a0ddd8;
    --hc-math: #bfc9f2;
    --hc-reading: #f5d08e;
    --astro: #7c3aed;
    --astro-soft: #ede9fe;
    --physics: #0e9aa7;
    --physics-soft: #e6f7f8;
    --math: #2f4ad0;
    --math-soft: #eef1fc;
    --reading: #d97706;
    --reading-soft: #fef3e2;
    --tools: #6d28d9;
    --tools-soft: #f3eafc;
}

[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;
    --shadow-card: 0 8px 24px -8px rgba(0, 0, 0, 0.6);
    --shadow-focus: 0 0 0 4px rgba(124, 143, 255, 0.18);
    --hero-bg: #141e0a;
    --highlight-bg: #1a1526;
    --hc-astro: #2d1f66;
    --hc-physics: #0c3632;
    --hc-math: #151d52;
    --hc-reading: #3d2805;
    --astro: #a78bfa;
    --astro-soft: #231e40;
    --physics: #2dd4bf;
    --physics-soft: #0e2422;
    --math: #7c8fff;
    --math-soft: #1c2244;
    --reading: #fbbf24;
    --reading-soft: #2c2006;
    --tools: #c4b5fd;
    --tools-soft: #211840;
}

* {
    box-sizing: border-box;
}

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

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

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

.skip-link {
    position: absolute;
    left: 16px;
    top: 16px;
    z-index: 10;
    background: var(--ink);
    color: var(--bg);
    padding: 10px 14px;
    border-radius: 8px;
    font-weight: 600;
    transform: translateY(-200%);
    transition: transform 120ms ease;
}

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

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

/* Nav */
.nav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    padding: 12px 0;
    border-bottom: 1px solid var(--line);
    margin-bottom: clamp(48px, 9vw, 96px);
}

.brand {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    font-weight: 600;
    font-size: 0.95rem;
    letter-spacing: -0.01em;
}

.brand-mark {
    display: inline-grid;
    place-items: center;
    width: 28px;
    height: 28px;
    border-radius: 8px;
    background: var(--ink);
    color: var(--bg);
    font-size: 13px;
}

.brand-dot {
    color: var(--ink-soft);
    margin: 0 2px;
}

/* Search (between hero and projects) */
.search-wrap {
    display: flex;
    justify-content: center;
    margin-bottom: clamp(32px, 5vw, 48px);
}

.hero-search {
    position: relative;
    width: 100%;
    max-width: 520px;
}

.hero-search-icon {
    position: absolute;
    left: 20px;
    top: 50%;
    transform: translateY(-50%);
    font-size: 16px;
    color: var(--ink-soft);
    pointer-events: none;
}

.hero-search-input {
    width: 100%;
    height: 56px;
    border: 1px solid var(--line-strong);
    border-radius: 14px;
    background: var(--surface);
    color: var(--ink);
    font: inherit;
    font-size: 1rem;
    padding: 10px 18px 10px 50px;
    transition: border-color 120ms ease, box-shadow 120ms ease;
}

.hero-search-input::placeholder {
    color: #9a9aa0;
}

.hero-search-input:focus {
    border-color: var(--ink);
    box-shadow: var(--shadow-focus);
    outline: 0;
}

.nav-actions {
    display: inline-flex;
    align-items: center;
    gap: 14px;
}

.nav-tag {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    font-size: 0.72rem;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    color: var(--ink-soft);
    font-weight: 600;
}

.nav-tag i {
    font-size: 12px;
}

/* Theme toggle */
.theme-toggle {
    display: inline-grid;
    place-items: center;
    width: 38px;
    height: 38px;
    padding: 0;
    border: 1px solid var(--line);
    border-radius: 50%;
    background: var(--surface-soft);
    color: var(--ink);
    cursor: pointer;
    font-size: 14px;
    transition: background 120ms ease, border-color 120ms ease, color 120ms ease;
}

.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;
}

/* Hero */
.hero {
    padding: clamp(36px, 6vw, 64px) clamp(28px, 5vw, 56px);
    background: var(--hero-bg);
    border-radius: 24px;
    margin: 0 0 clamp(36px, 6vw, 56px);
}

.hero-content {
    flex: 1;
    min-width: 0;
}

.hero-title {
    margin: 0;
    font-weight: 600;
    font-size: clamp(2.4rem, 7.5vw, 5rem);
    line-height: 1.02;
    letter-spacing: -0.035em;
    color: var(--ink);
}

.hero-lede {
    margin: 24px 0 0;
    font-size: clamp(1.05rem, 1.4vw, 1.2rem);
    color: var(--ink-soft);
    line-height: 1.5;
}

.hero-visual {
    display: none;
    position: relative;
    width: 240px;
    height: 220px;
    flex-shrink: 0;
}

.hero-visual-circle {
    position: absolute;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    font-size: 28px;
    transition: transform 200ms ease;
}

.hero-visual-circle svg {
    width: 28px;
    height: 28px;
}

.hero-visual-circle--astro {
    width: 90px;
    height: 90px;
    top: 0;
    left: 30px;
    background: var(--hc-astro);
    color: var(--astro);
}

.hero-visual-circle--physics {
    width: 76px;
    height: 76px;
    top: 16px;
    right: 0;
    background: var(--hc-physics);
    color: var(--physics);
}

.hero-visual-circle--math {
    width: 82px;
    height: 82px;
    bottom: 0;
    left: 0;
    background: var(--hc-math);
    color: var(--math);
}

.hero-visual-circle--reading {
    width: 70px;
    height: 70px;
    bottom: 20px;
    right: 16px;
    background: var(--hc-reading);
    color: var(--reading);
}

.hero-layout {
    display: flex;
    align-items: center;
    gap: clamp(32px, 5vw, 56px);
}

@media (min-width: 760px) {
    .hero-visual {
        display: block;
    }
}

/* Projects section */
.projects-section {
    padding-top: clamp(28px, 4vw, 40px);
    border-top: 1px solid var(--line);
}

.projects-section--highlight {
    margin-top: clamp(32px, 5vw, 56px);
    background: var(--highlight-bg);
    border-radius: 24px;
    padding: clamp(28px, 4vw, 40px) clamp(24px, 4vw, 40px);
    border: 1px solid var(--line);
}

.projects-head {
    display: flex;
    align-items: baseline;
    justify-content: space-between;
    gap: 16px;
    margin-bottom: 28px;
}

.projects-head h2 {
    margin: 0;
    font-size: clamp(1.3rem, 2vw, 1.6rem);
    font-weight: 600;
    letter-spacing: -0.02em;
}

.projects-count {
    font-size: 0.85rem;
    color: var(--ink-soft);
}

/* Grid */
.grid {
    list-style: none;
    margin: 0;
    padding: 0;
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 16px;
}

.card {
    background: var(--surface);
}

.card a,
.card-inner {
    display: flex;
    flex-direction: column;
    height: 100%;
    min-height: 280px;
    padding: 22px;
    border: 1px solid var(--line);
    border-radius: 16px;
    background: var(--surface);
    transition: border-color 160ms ease, transform 160ms ease, box-shadow 160ms ease;
}

.card a {
    cursor: pointer;
}

.card a:hover,
.card a:focus-visible {
    border-color: var(--ink);
    transform: translateY(-2px);
    box-shadow: var(--shadow-card);
    outline: 0;
}

.card a:hover .card-arrow,
.card a:focus-visible .card-arrow {
    background: var(--accent);
    color: var(--bg);
    transform: translate(2px, -2px);
}

.card-top {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 24px;
}

.card-icon {
    display: inline-grid;
    place-items: center;
    width: 44px;
    height: 44px;
    border-radius: 12px;
    background: var(--accent-soft);
    color: var(--accent);
    font-size: 18px;
    transition: background 160ms ease, color 160ms ease, transform 160ms ease;
}

.card-num {
    display: inline-grid;
    place-items: center;
    min-width: 34px;
    height: 26px;
    padding: 0 10px;
    border-radius: 999px;
    background: var(--surface-soft);
    color: var(--ink-soft);
    font-size: 0.78rem;
    font-weight: 700;
    letter-spacing: 0.04em;
    border: 1px solid var(--line);
}

.card-arrow {
    margin-left: auto;
    display: inline-grid;
    place-items: center;
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: var(--surface-soft);
    color: var(--ink);
    font-size: 14px;
    transition: background 160ms ease, color 160ms ease, transform 160ms ease;
}

.card a:hover .card-icon,
.card a:focus-visible .card-icon {
    background: var(--accent);
    color: var(--bg);
}

.card-badge {
    margin-left: auto;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    font-size: 0.72rem;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--ink-soft);
    border: 1px solid var(--line-strong);
    padding: 4px 10px;
    border-radius: 999px;
    font-weight: 600;
}

.card-body {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.card-tag {
    font-size: 0.72rem;
    letter-spacing: 0.14em;
    text-transform: uppercase;
    color: var(--ink-soft);
    font-weight: 600;
}

.card-title {
    margin: 0;
    font-size: clamp(1.5rem, 2.5vw, 1.85rem);
    font-weight: 600;
    letter-spacing: -0.025em;
    line-height: 1.1;
}

.card-desc {
    margin: 0;
    color: var(--ink-soft);
    font-size: 0.95rem;
    line-height: 1.5;
}

.card-foot {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    margin-top: 22px;
    padding-top: 18px;
    border-top: 1px dashed var(--line);
}

.card-foot span {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    font-size: 0.75rem;
    color: var(--ink-soft);
    padding: 4px 10px;
    background: var(--surface-soft);
    border-radius: 999px;
}

.card-foot i {
    font-size: 10px;
    color: var(--accent);
}

.card-soon {
    opacity: 0.85;
}

.card-soon .card-inner {
    background: var(--surface-soft);
    border-style: dashed;
}

.card-soon .card-num {
    background: #efefef;
    color: var(--ink-soft);
}

.card-soon .card-icon {
    background: #f0f0f0;
    color: var(--ink-soft);
}

.card-icon--astro {
    background: var(--astro-soft);
    color: var(--astro);
}

.card-icon--physics {
    background: var(--physics-soft);
    color: var(--physics);
}

.card-icon--math {
    background: var(--math-soft);
    color: var(--math);
}

.card-icon--reading {
    background: var(--reading-soft);
    color: var(--reading);
}

.card-icon--tools {
    background: var(--tools-soft);
    color: var(--tools);
}

.card a:hover .card-icon--astro,
.card a:focus-visible .card-icon--astro {
    background: var(--astro);
    color: var(--bg);
}

.card a:hover .card-icon--physics,
.card a:focus-visible .card-icon--physics {
    background: var(--physics);
    color: var(--bg);
}

.card a:hover .card-icon--math,
.card a:focus-visible .card-icon--math {
    background: var(--math);
    color: var(--bg);
}

.card a:hover .card-icon--reading,
.card a:focus-visible .card-icon--reading {
    background: var(--reading);
    color: var(--bg);
}

.card a:hover .card-icon--tools,
.card a:focus-visible .card-icon--tools {
    background: var(--tools);
    color: var(--bg);
}

.card-foot--astro i { color: var(--astro); }
.card-foot--physics i { color: var(--physics); }
.card-foot--math i { color: var(--math); }
.card-foot--reading i { color: var(--reading); }
.card-foot--tools i { color: var(--tools); }

/* Empty state */
.empty {
    grid-column: 1 / -1;
    margin: 24px 0 0;
    padding: 24px;
    text-align: center;
    color: var(--ink-soft);
    border: 1px dashed var(--line-strong);
    border-radius: 14px;
    background: var(--surface-soft);
}

/* Footer */
.foot {
    margin-top: 96px;
    padding-top: 24px;
    border-top: 1px solid var(--line);
    display: flex;
    justify-content: space-between;
    gap: 16px;
    font-size: 0.85rem;
    color: var(--ink-soft);
}

/* Responsive */
@media (max-width: 760px) {
    .nav {
        margin-bottom: 48px;
    }

    .hero-search-input {
        height: 52px;
    }

    .hero {
        padding: clamp(24px, 5vw, 36px) clamp(20px, 4vw, 32px);
        border-radius: 18px;
    }

    .hero-visual {
        display: none;
    }

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

    .card a,
    .card-inner {
        min-height: 240px;
    }
}