/* ─────────────────────────────────────────────────────────────
   Superluminal — Relativistic Kinematics at Constant Proper
   Acceleration. Dark space theme, single-page layout.
   ───────────────────────────────────────────────────────────── */

:root {
    --bg: #05080f;
    --bg-elevated: #0b1220;
    --bg-card: #0e1626;
    --panel: rgba(14, 22, 38, 0.72);
    --border: #1c2838;
    --border-soft: rgba(56, 189, 248, 0.16);

    --text: #e7eef7;
    --text-muted: #93a1b4;
    --text-faint: #66768a;

    --amber: #f0b429;
    --amber-soft: rgba(240, 180, 41, 0.12);
    --sky: #38bdf8;
    --sky-soft: rgba(56, 189, 248, 0.10);
    --violet: #a78bfa;
    --green: #34d399;

    --serif: "Iowan Old Style", "Palatino Linotype", "Book Antiqua", Palatino, Georgia, serif;
    --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    --mono: "SF Mono", "JetBrains Mono", "Fira Code", Menlo, Consolas, monospace;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
    margin: 0;
    font-family: var(--sans);
    color: var(--text);
    background:
        radial-gradient(1.2px 1.2px at 12% 22%, rgba(255,255,255,.55), transparent 55%),
        radial-gradient(1px 1px at 34% 8%, rgba(255,255,255,.35), transparent 55%),
        radial-gradient(1.4px 1.4px at 58% 30%, rgba(255,255,255,.45), transparent 55%),
        radial-gradient(1px 1px at 76% 12%, rgba(255,255,255,.4), transparent 55%),
        radial-gradient(1.3px 1.3px at 88% 42%, rgba(255,255,255,.5), transparent 55%),
        radial-gradient(1px 1px at 22% 62%, rgba(255,255,255,.35), transparent 55%),
        radial-gradient(1.2px 1.2px at 48% 74%, rgba(255,255,255,.4), transparent 55%),
        radial-gradient(1px 1px at 68% 58%, rgba(255,255,255,.3), transparent 55%),
        radial-gradient(1.4px 1.4px at 8% 82%, rgba(255,255,255,.35), transparent 55%),
        radial-gradient(1px 1px at 92% 78%, rgba(255,255,255,.4), transparent 55%),
        linear-gradient(180deg, #05080f 0%, #090f1d 55%, #0c1428 100%);
    background-attachment: fixed;
    line-height: 1.65;
    font-size: 17px;
    -webkit-font-smoothing: antialiased;
}

a { color: var(--sky); text-decoration: none; }
a:hover { text-decoration: underline; }

::selection { background: rgba(240, 180, 41, 0.28); }

.container { max-width: 1060px; margin: 0 auto; padding: 3.5rem 1.5rem; }

/* ── Header ─────────────────────────────────────────────── */
header {
    position: sticky;
    top: 0;
    z-index: 50;
    background: rgba(5, 8, 15, 0.82);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border);
}
.header-inner {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0.8rem 1.5rem;
    display: flex;
    align-items: center;
    gap: 1.5rem;
    flex-wrap: wrap;
}
.header-brand { display: flex; align-items: baseline; gap: 0.75rem; }
.header-logo {
    font-family: var(--serif);
    font-size: 1.35rem;
    font-weight: 700;
    color: var(--amber);
    letter-spacing: 0.02em;
}
.header-subtitle { font-size: 0.82rem; color: var(--text-muted); }
header nav { margin-left: auto; }
header nav ul { display: flex; gap: 1.4rem; list-style: none; margin: 0; padding: 0; flex-wrap: wrap; }
header nav a { color: var(--text-muted); font-size: 0.9rem; font-weight: 500; }
header nav a:hover { color: var(--amber); text-decoration: none; }

/* ── Hero ──────────────────────────────────────────────── */
.hero {
    position: relative;
    padding: 5rem 1.5rem 4rem;
    text-align: center;
    overflow: hidden;
    border-bottom: 1px solid var(--border);
    background:
        radial-gradient(60% 90% at 50% -10%, rgba(56, 189, 248, 0.10), transparent 70%),
        radial-gradient(40% 70% at 50% 110%, rgba(240, 180, 41, 0.08), transparent 70%);
}
.hero-eyebrow {
    display: inline-block;
    font-size: 0.78rem;
    letter-spacing: 0.22em;
    text-transform: uppercase;
    color: var(--sky);
    border: 1px solid var(--border-soft);
    padding: 0.35rem 0.9rem;
    border-radius: 999px;
    margin-bottom: 1.5rem;
}
.hero h1 {
    font-family: var(--serif);
    font-size: clamp(2.6rem, 7vw, 4.6rem);
    margin: 0 0 0.75rem;
    font-weight: 700;
    letter-spacing: 0.01em;
    background: linear-gradient(120deg, #fff 20%, var(--amber) 55%, var(--sky) 90%);
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
}
.hero h2 {
    font-size: clamp(1.05rem, 2.6vw, 1.45rem);
    font-weight: 400;
    color: var(--text-muted);
    margin: 0 0 2rem;
    font-style: italic;
}
.hero-stats {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 1rem;
    max-width: 880px;
    margin: 0 auto;
}
.hero-stat {
    background: var(--panel);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1.1rem 0.8rem;
}
.hero-stat .num {
    display: block;
    font-family: var(--serif);
    font-size: 1.7rem;
    font-weight: 700;
    color: var(--amber);
}
.hero-stat .lbl { display: block; font-size: 0.78rem; color: var(--text-muted); margin-top: 0.2rem; }

/* ── Section scaffolding ──────────────────────────────── */
section h2 {
    font-family: var(--serif);
    font-size: 2rem;
    margin: 0 0 1.5rem;
    font-weight: 700;
}
.section-intro { color: var(--text-muted); font-size: 1.05rem; max-width: 760px; margin-bottom: 2rem; }
.accent-bar {
    display: inline-block;
    width: 34px;
    height: 4px;
    background: linear-gradient(90deg, var(--amber), var(--sky));
    border-radius: 2px;
    margin-right: 0.6rem;
    vertical-align: middle;
}
.divider { border: none; border-top: 1px solid var(--border); margin: 0; }
.bg-alt { background: rgba(11, 18, 32, 0.45); border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); }

/* ── Cards ────────────────────────────────────────────── */
.cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 1.25rem; }
.card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-top: 3px solid var(--amber);
    border-radius: 12px;
    padding: 1.5rem 1.5rem 1.35rem;
}
.card.sky { border-top-color: var(--sky); }
.card.violet { border-top-color: var(--violet); }
.card h3 { font-size: 1.12rem; margin: 0 0 0.6rem; font-weight: 650; }
.card p { color: var(--text-muted); font-size: 0.94rem; margin: 0 0 0.4rem; }
.card .tag {
    display: inline-block;
    font-size: 0.72rem;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--text-faint);
    border: 1px solid var(--border);
    border-radius: 999px;
    padding: 0.15rem 0.55rem;
    margin-bottom: 0.7rem;
}

/* ── Formulas ─────────────────────────────────────────── */
.formula {
    background: var(--bg-elevated);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1.6rem 1.2rem;
    margin: 1.25rem 0;
    text-align: center;
    font-family: var(--serif);
    font-size: 1.35rem;
    overflow-x: auto;
    white-space: nowrap;
}
.formula .fname { font-style: italic; color: var(--sky); }
.formula .sub { font-size: 0.62em; vertical-align: sub; color: var(--text-muted); }
.formula .op { color: var(--text-faint); margin: 0 0.35em; }
.frac { display: inline-flex; flex-direction: column; vertical-align: middle; text-align: center; margin: 0 0.18em; line-height: 1.05; }
.frac .num { padding: 0 0.3em 0.15em; border-bottom: 1.4px solid var(--text-muted); }
.frac .den { padding: 0.15em 0.3em 0; }
.formula .note { display: block; font-family: var(--sans); font-size: 0.8rem; color: var(--text-faint); margin-top: 1rem; font-style: italic; }

/* ── Tables ───────────────────────────────────────────── */
.table-wrap { overflow-x: auto; border: 1px solid var(--border); border-radius: 12px; }
table { width: 100%; border-collapse: collapse; font-size: 0.92rem; }
thead th {
    background: #0e1830;
    color: var(--text);
    text-align: left;
    padding: 0.8rem 1rem;
    font-weight: 650;
    border-bottom: 1px solid var(--border);
    white-space: nowrap;
}
tbody td { padding: 0.8rem 1rem; border-bottom: 1px solid var(--border); color: var(--text-muted); vertical-align: top; }
tbody tr:last-child td { border-bottom: none; }
tbody tr:hover { background: rgba(56, 189, 248, 0.05); }
tbody td strong { color: var(--text); }
.mono { font-family: var(--mono); font-size: 0.9em; color: var(--amber); }

/* ── Callout / highlight ─────────────────────────────── */
.callout {
    background: linear-gradient(135deg, var(--amber-soft), rgba(240, 180, 41, 0.04));
    border: 1px solid rgba(240, 180, 41, 0.35);
    border-radius: 12px;
    padding: 1.4rem 1.6rem;
    margin: 1.5rem 0;
}
.callout.sky {
    background: linear-gradient(135deg, var(--sky-soft), rgba(56, 189, 248, 0.04));
    border-color: var(--border-soft);
}
.callout strong { color: var(--text); }

/* ── Minkowski diagram ───────────────────────────────── */
.diagram {
    background: var(--bg-elevated);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1.4rem;
    margin: 1.5rem 0;
}
.diagram svg { width: 100%; height: auto; display: block; }
.diagram figcaption { text-align: center; color: var(--text-muted); font-size: 0.85rem; margin-top: 0.9rem; }

/* ── Calculator ──────────────────────────────────────── */
.calc {
    display: grid;
    grid-template-columns: 320px 1fr;
    gap: 1.5rem;
    margin-top: 1.5rem;
}
.calc-form {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1.5rem;
}
.calc-form label { display: block; font-size: 0.85rem; color: var(--text-muted); margin-bottom: 0.35rem; }
.calc-form input[type="range"] { width: 100%; accent-color: var(--amber); }
.calc-form .value {
    display: flex;
    justify-content: space-between;
    font-family: var(--mono);
    font-size: 0.92rem;
    color: var(--amber);
    margin-bottom: 1.25rem;
}
.calc-form .value span:last-child { font-weight: 700; }
.calc-results { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; align-content: start; }
.result {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 1.2rem 1.3rem;
}
.result .lbl { font-size: 0.78rem; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.06em; }
.result .val { font-family: var(--serif); font-size: 1.6rem; font-weight: 700; color: var(--amber); margin-top: 0.35rem; }
.result .unit { font-size: 0.85rem; color: var(--text-faint); margin-left: 0.3rem; font-family: var(--sans); font-weight: 400; }
.result .hint { font-size: 0.8rem; color: var(--text-faint); margin-top: 0.35rem; }
.result.hl { border-color: rgba(240, 180, 41, 0.45); background: linear-gradient(135deg, var(--amber-soft), var(--bg-card)); }
.result.hl .val { color: #fff; }
.calc-note { font-size: 0.82rem; color: var(--text-faint); margin-top: 1.2rem; grid-column: 1 / -1; }

/* ── Footer ──────────────────────────────────────────── */
footer {
    border-top: 1px solid var(--border);
    padding: 2.5rem 1.5rem 3rem;
    text-align: center;
    font-size: 0.85rem;
    color: var(--text-muted);
}
footer .footer-impressum { margin-bottom: 1rem; }
footer .footer-impressum strong { color: var(--text); }
footer a { color: var(--text-muted); }
footer a:hover { color: var(--amber); }

/* ── Legal pages ─────────────────────────────────────── */
.legal-page { max-width: 780px; margin: 0 auto; padding: 3rem 1.5rem 4rem; }
.legal-page h1 { font-family: var(--serif); font-size: 2.2rem; }
.legal-page h2 { font-size: 1.15rem; margin-top: 2rem; color: var(--amber); }

/* ── Responsive ──────────────────────────────────────── */
@media (max-width: 760px) {
    .calc { grid-template-columns: 1fr; }
    .calc-results { grid-template-columns: 1fr; }
    .header-inner { justify-content: center; text-align: center; }
    header nav { margin-left: 0; width: 100%; justify-content: center; }
    header nav ul { justify-content: center; }
}