:root {
    --bg: #eceae6;
    --paper: #faf9f7;
    --ink: #1c1b19;
    --ink-muted: #5c5954;
    --border: #d9d5ce;
    --accent: #1f4e46;
    --accent-dark: #163832;
    --accent-soft: #e4efec;
    --link: #1a5f8a;
    --code-bg: #f0eeea;
    --shadow: 0 1px 2px rgba(28, 27, 25, 0.06), 0 8px 24px rgba(28, 27, 25, 0.06);
    --measure: 52.5rem;
    --ui: "IBM Plex Sans", system-ui, sans-serif;
    --serif: "Source Serif 4", "Iowan Old Style", Georgia, serif;
    --mono: "IBM Plex Mono", ui-monospace, monospace;
    --jump-h: 5.5rem;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
    margin: 0;
    min-height: 100vh;
    font-family: var(--serif);
    font-size: 1.125rem;
    line-height: 1.75;
    color: var(--ink);
    background:
        radial-gradient(1200px 600px at 10% -10%, #e7ebe8 0%, transparent 55%),
        radial-gradient(900px 500px at 100% 0%, #e9e4dc 0%, transparent 50%),
        var(--bg);
    -webkit-font-smoothing: antialiased;
}
a { color: var(--link); text-underline-offset: 2px; }

/* language rail */
.lang-rail {
    position: fixed;
    right: 0;
    top: 50%;
    transform: translateY(-50%);
    z-index: 40;
    display: flex;
    flex-direction: column;
    background: var(--paper);
    border: 1px solid var(--border);
    border-right: 0;
    border-radius: 10px 0 0 10px;
    box-shadow: var(--shadow);
    overflow: hidden;
}
.lang-rail button {
    appearance: none;
    border: 0;
    background: transparent;
    font-family: var(--ui);
    font-weight: 600;
    font-size: 0.85rem;
    padding: 0.65rem 0.7rem;
    color: var(--ink-muted);
    cursor: pointer;
}
.lang-rail button + button { border-top: 1px solid var(--border); }
.lang-rail button[aria-pressed="true"] { background: var(--accent); color: #fff; }

/* top bar */
.topbar {
    position: sticky;
    top: 0;
    z-index: 20;
    backdrop-filter: saturate(1.2) blur(10px);
    background: rgba(250, 249, 247, 0.94);
    border-bottom: 1px solid var(--border);
}
.jumpbar {
    padding: 0.3rem 3.2rem 0.35rem 0.4rem;
    display: flex;
    flex-wrap: wrap;
    gap: 0.2rem;
    align-items: center;
}
.jump, .home {
    appearance: none;
    border: 1px solid var(--border);
    background: #ebe8e2;
    color: var(--ink-muted);
    font-family: var(--ui);
    font-size: 0.86rem;
    font-weight: 600;
    line-height: 1.15;
    padding: 0.28rem 0.58rem;
    border-radius: 999px;
    white-space: nowrap;
    cursor: pointer;
    text-decoration: none;
}
.jump:hover { color: var(--ink); background: var(--paper); }
.jump[aria-current="true"] { background: var(--paper); color: var(--accent); }
.home { background: var(--accent); color: #fff; border-color: var(--accent); }
.home:hover { background: var(--accent-dark); }
.jump-toggle { display: none; }
.fab-top {
    position: fixed;
    right: 1.1rem;
    bottom: 1.1rem;
    z-index: 30;
    appearance: none;
    border: 0;
    background: var(--accent);
    color: #fff;
    font-family: var(--ui);
    font-size: 0.8rem;
    font-weight: 600;
    padding: 0.7rem 0.95rem;
    border-radius: 999px;
    cursor: pointer;
    box-shadow: 0 8px 20px rgba(28, 27, 25, 0.18);
}
.fab-top[hidden] { display: none; }

main { max-width: 70rem; margin: 0 auto; padding: 1.5rem 3.2rem 4rem 1.25rem; }
.sheet {
    background: var(--paper);
    border: 1px solid var(--border);
    border-radius: 14px;
    box-shadow: var(--shadow);
    padding: clamp(1.5rem, 4vw, 3rem) clamp(1.25rem, 4vw, 3.25rem);
    min-height: 70vh;
}
.doc-meta {
    font-family: var(--ui);
    font-size: 0.8rem;
    color: var(--ink-muted);
    margin: 0 0 1.25rem;
    padding-bottom: 1rem;
    border-bottom: 1px solid var(--border);
    display: flex;
    justify-content: space-between;
    gap: 1rem;
    flex-wrap: wrap;
}

/* markdown */
#doc { max-width: var(--measure); margin: 0 auto; }
#doc :is(h1, h2, h3, h4), #doc a[id] { scroll-margin-top: var(--jump-h); }
#doc a[id] { display: block; }
#doc :is(h1, h2, h3, h4) { font-weight: 700; line-height: 1.25; letter-spacing: -0.01em; }
#doc h1 { font-size: clamp(1.7rem, 3vw, 2.15rem); margin: 0 0 0.85em; padding-bottom: 0.35em; border-bottom: 1px solid var(--border); }
#doc h2 { font-size: 1.4rem; margin: 1.8em 0 0.55em; }
#doc h3 { font-size: 1.18rem; margin: 1.45em 0 0.4em; }
#doc h4 { font-size: 1.05rem; margin: 1.25em 0 0.35em; }
#doc p { margin: 0.85em 0; }
#doc blockquote { margin: 1.1em 0; padding: 0.15em 0 0.15em 1em; color: #34322e; border-left: 3px solid var(--accent); background: linear-gradient(90deg, var(--accent-soft), transparent 70%); }
#doc ul, #doc ol { margin: 0.85em 0; padding-left: 1.35em; }
#doc li { margin: 0.35em 0; }
#doc hr { border: none; border-top: 1px solid var(--border); margin: 2.2em 0; }
#doc table { width: 100%; border-collapse: collapse; font-family: var(--ui); font-size: 0.92rem; line-height: 1.45; margin: 1.2em 0; display: block; overflow-x: auto; }
#doc th, #doc td { border: 1px solid var(--border); padding: 0.55rem 0.75rem; text-align: left; vertical-align: top; }
#doc th { background: var(--code-bg); font-weight: 600; }
#doc pre { font-family: var(--mono); font-size: 0.8rem; line-height: 1.55; background: var(--code-bg); border: 1px solid var(--border); border-radius: 8px; padding: 0.95rem 1.05rem; overflow-x: auto; margin: 1.1em 0; }
#doc code { font-family: var(--mono); font-size: 0.86em; }
#doc :not(pre) > code { background: var(--accent-soft); color: var(--accent); padding: 0.12em 0.38em; border-radius: 4px; }
#err { margin: 0 0 1rem; padding: 0.9rem 1rem; background: #f8ecec; border: 1px solid #e2b6b6; border-radius: 8px; color: #7a1f1f; font-family: var(--ui); }
#err[hidden] { display: none; }
.loading { font-family: var(--ui); color: var(--ink-muted); }

/* landing */
.hero h1 { font-size: clamp(1.8rem, 3.4vw, 2.4rem); margin: 0 0 0.3em; }
.hero p { color: var(--ink-muted); margin: 0 0 1.6rem; }
.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr)); gap: 1rem; }
.card {
    display: block;
    text-decoration: none;
    color: var(--ink);
    background: #fff;
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1.2rem 1.3rem 1.3rem;
    box-shadow: var(--shadow);
    transition: transform 0.12s ease, border-color 0.12s ease;
}
.card:hover { transform: translateY(-2px); border-color: var(--accent); }
.card .tag { font-family: var(--ui); font-size: 0.75rem; font-weight: 600; text-transform: uppercase; letter-spacing: 0.06em; color: var(--accent); }
.card h2 { font-size: 1.3rem; margin: 0.25em 0 0.35em; }
.card p { font-size: 0.98rem; line-height: 1.55; color: var(--ink-muted); margin: 0; }
.core {
    margin: 2rem 0 0;
    padding: 1rem 1.2rem;
    border-left: 3px solid var(--accent);
    background: var(--accent-soft);
    border-radius: 0 10px 10px 0;
}
.core .label { font-family: var(--ui); font-size: 0.78rem; font-weight: 600; color: var(--accent); text-transform: uppercase; letter-spacing: 0.06em; }

@media (max-width: 640px) {
    body { font-size: 1.05rem; line-height: 1.7; }
    :root { --jump-h: 6.5rem; }
    .jump { font-size: 0.8rem; padding: 0.24rem 0.5rem; }
    .jump-toggle { display: inline-flex; background: var(--accent); color: #fff; border-color: var(--accent); }
    .topbar.is-collapsed .jump:not(.jump-toggle) { display: none; }
    main { padding: 1rem 2.9rem 3rem 0.6rem; }
    .sheet { border-radius: 10px; }
}