:root {
    --bg: #ddd7cb;
    --surface: rgba(255, 255, 255, 0.92);
    --surface-strong: #ffffff;
    --line: rgba(10, 13, 16, 0.22);
    --line-strong: rgba(10, 13, 16, 0.42);
    --text: #0f1215;
    --muted: #353d46;
    --shadow: 0 18px 40px rgba(0, 0, 0, 0.12);
    --panel-shadow: 0 10px 24px rgba(0, 0, 0, 0.08);
    --intro: #845ec2;
    --motion: #ef7d57;
    --mechanics: #307351;
    --sensors: #2d6cdf;
    --code: #6b7280;
    --spike: #1296a3;
    --links: #2e9e4f;
}

*,
*::before,
*::after {
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    margin: 0;
    min-width: 320px;
    color: var(--text);
    font-family: "Manrope", sans-serif;
    background:
        radial-gradient(circle at top left, rgba(132, 94, 194, 0.1), transparent 26%),
        radial-gradient(circle at top right, rgba(18, 150, 163, 0.08), transparent 20%),
        linear-gradient(180deg, #ece7de 0%, var(--bg) 100%);
}

a {
    color: inherit;
}

.page-shell {
    width: min(1320px, calc(100% - 20px));
    margin: 0 auto;
    padding: 10px 0 20px;
}

.site-header {
    margin-bottom: 10px;
    padding: 2px 2px 0;
}

.site-header h1,
.library-card h2 {
    margin: 0;
    font-family: "Space Grotesk", sans-serif;
    letter-spacing: -0.04em;
}

.site-header h1 {
    font-size: clamp(1.7rem, 2.5vw, 2.25rem);
    line-height: 1;
}

.library-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 12px;
}

.library-card {
    position: relative;
    padding: 14px;
    border: 2px solid var(--line);
    border-radius: 16px;
    background: var(--surface-strong);
    box-shadow: var(--shadow);
    overflow: hidden;
}

.library-card::before {
    content: "";
    position: absolute;
    inset: 0 0 auto;
    height: 4px;
    background: var(--accent, var(--line-strong));
}

.library-card--intro { --accent: var(--intro); }
.library-card--motion { --accent: var(--motion); }
.library-card--mechanics { --accent: var(--mechanics); }
.library-card--sensors { --accent: var(--sensors); }
.library-card--code { --accent: var(--code); }
.library-card--spike { --accent: var(--spike); }
.library-card--links { --accent: var(--links); }

.section-header {
    margin-bottom: 10px;
}

.section-header h2 {
    font-size: 1.55rem;
}

.resource-group + .resource-group {
    margin-top: 12px;
}

.resource-group h3 {
    margin: 0 0 8px;
    font-size: 0.82rem;
    font-weight: 800;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--muted);
}

.resource-list {
    list-style: none;
    margin: 0;
    padding: 0;
    display: grid;
    gap: 6px;
}

.book-list {
    list-style: none;
    margin: 0;
    padding: 0;
    display: grid;
    gap: 8px;
}

.book-item {
    position: relative;
    display: grid;
    gap: 3px;
    padding: 10px 12px 10px 14px;
    border: 1px solid rgba(10, 13, 16, 0.12);
    border-radius: 12px;
    background: linear-gradient(180deg, rgba(255, 255, 255, 0.74), rgba(246, 241, 233, 0.92));
}

.book-item::before {
    content: "";
    position: absolute;
    left: 0;
    top: 9px;
    bottom: 9px;
    width: 4px;
    border-radius: 999px;
    background: var(--mechanics);
}

.book-author {
    color: var(--muted);
    font-size: 0.72rem;
    font-weight: 800;
    letter-spacing: 0.08em;
    text-transform: uppercase;
}

.book-title {
    color: var(--text);
    font-size: 1rem;
    font-weight: 800;
    line-height: 1.25;
}

.resource-item {
    display: grid;
    gap: 6px;
    padding: 7px 8px 8px;
    border: 1px solid rgba(10, 13, 16, 0.12);
    border-radius: 12px;
    background: rgba(255, 255, 255, 0.48);
    box-shadow: none;
}

.resource-copy h4 {
    margin: 0 0 1px 2px;
    font-size: 0.9rem;
    font-weight: 800;
    line-height: 1.2;
}

.resource-actions {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}

.action {
    display: inline-flex;
    align-items: center;
    justify-content: flex-start;
    width: fit-content;
    min-height: 36px;
    max-width: 100%;
    padding: 0 15px;
    border: 1px solid transparent;
    border-radius: 11px;
    text-decoration: none;
    text-align: left;
    font-size: 0.92rem;
    font-weight: 800;
    line-height: 1.2;
    transition: transform 160ms ease, border-color 160ms ease, background-color 160ms ease, color 160ms ease;
}

.action:hover,
.action:focus-visible {
    transform: translateY(-1px);
}

.action:focus-visible {
    outline: 2px solid rgba(45, 108, 223, 0.26);
    outline-offset: 3px;
}

.action--primary {
    border-color: #1296ef;
    background: #1296ef;
    color: #fff;
}

.action--download {
    border-color: #77808a;
    background: #77808a;
    color: #fff;
}

.action--external {
    border-color: #2e9e4f;
    background: #2e9e4f;
    color: #fff;
}

@media (max-width: 640px) {
    .page-shell {
        width: min(100% - 12px, 1240px);
        padding: 8px 0 16px;
    }

    .library-card {
        padding: 12px;
        border-radius: 14px;
    }

    .site-header h1 {
        font-size: 1.85rem;
    }

    .section-header h2 {
        font-size: 1.35rem;
    }

    .action {
        width: 100%;
    }
}