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

:root {
  --bg:         #ffffff;
  --bg-alt:     #f6f8fa;
  --text:       #1a1a1a;
  --text-muted: #555;
  --border:     #d0d7de;
  --accent:     #1B4F72;
  --accent-2:   #2E86C1;
  --red:        #C0392B;
  --green:      #1E8449;
  --amber:      #D68910;
  --code-bg:    #f0f2f4;
  --radius:     6px;
  --max-w:      780px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg:         #0d1117;
    --bg-alt:     #161b22;
    --text:       #e6edf3;
    --text-muted: #8b949e;
    --border:     #30363d;
    --accent:     #58a6ff;
    --accent-2:   #79c0ff;
    --code-bg:    #1f2428;
  }
}

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial,
               sans-serif, "Apple Color Emoji";
  font-size: 17px;
  line-height: 1.65;
  color: var(--text);
  background: var(--bg);
}

/* ── Layout ─────────────────────────────────────────────────────────────── */
.container {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 20px;
}

section {
  padding: 56px 0;
  border-top: 1px solid var(--border);
}

section:first-of-type { border-top: none; }

/* ── Typography ──────────────────────────────────────────────────────────── */
h1 { font-size: clamp(1.6rem, 4vw, 2.4rem); line-height: 1.2; font-weight: 700; }
h2 { font-size: 1.4rem; font-weight: 700; margin-bottom: 16px; color: var(--accent); }
h3 { font-size: 1.1rem; font-weight: 600; margin-bottom: 8px; }
p  { margin-bottom: 14px; }
p:last-child { margin-bottom: 0; }

a { color: var(--accent-2); text-decoration: underline; }
a:hover { opacity: 0.8; }

/* ── Masthead ────────────────────────────────────────────────────────────── */
.masthead {
  padding: 48px 0 40px;
  border-top: none;
}

.masthead-inner {
  display: flex;
  gap: 36px;
  align-items: flex-start;
}

.cover-link {
  flex: 0 0 auto;
  display: block;
  text-decoration: none;
}

.cover-img {
  width: 190px;
  border-radius: 4px;
  box-shadow: 0 4px 20px rgba(0,0,0,0.25);
  display: block;
  transition: box-shadow 0.2s, transform 0.2s;
}

.cover-img:hover {
  box-shadow: 0 8px 32px rgba(0,0,0,0.35);
  transform: translateY(-2px);
}

.masthead-text {
  flex: 1 1 auto;
  min-width: 0;
}

.masthead .meta {
  margin: 12px 0 24px;
  color: var(--text-muted);
  font-size: 0.95rem;
}

.masthead .meta a { color: var(--text-muted); }

.badge {
  display: inline-block;
  padding: 3px 10px;
  background: var(--accent);
  color: #fff;
  border-radius: 20px;
  font-size: 0.78rem;
  font-weight: 600;
  letter-spacing: 0.03em;
  text-decoration: none;
  vertical-align: middle;
  margin-left: 6px;
}

.button-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 20px;
}

.btn {
  display: inline-block;
  padding: 9px 20px;
  border-radius: var(--radius);
  font-size: 0.9rem;
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  border: none;
  transition: opacity 0.15s;
}

.btn:hover { opacity: 0.85; }

.btn-primary {
  background: var(--accent);
  color: #fff;
}

.btn-secondary {
  background: transparent;
  color: var(--accent-2);
  border: 1.5px solid var(--border);
}

/* ── Formula block ───────────────────────────────────────────────────────── */
.formula-block {
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px 28px;
  margin: 24px 0;
  text-align: center;
  font-size: 1.05rem;
  overflow-x: auto;
}

/* ── Hero figure ─────────────────────────────────────────────────────────── */
.hero-fig {
  margin: 24px 0;
}

.hero-fig img {
  width: 100%;
  height: auto;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  display: block;
}

/* ── R_eff explorer widget ───────────────────────────────────────────────── */
#reff-explorer {
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px 28px;
  margin: 24px 0;
}

#reff-explorer h3 { margin-bottom: 16px; }

.slider-row {
  display: grid;
  grid-template-columns: 120px 1fr 60px;
  align-items: center;
  gap: 12px;
  margin-bottom: 10px;
}

.slider-row label { font-size: 0.9rem; }
.slider-row input[type=range] { width: 100%; }
.slider-row .val { text-align: right; font-size: 0.9rem; font-variant-numeric: tabular-nums; }

#reff-result {
  margin-top: 20px;
  padding: 14px 18px;
  border-radius: var(--radius);
  font-weight: 600;
  font-size: 1rem;
  text-align: center;
}

#reff-result.damped     { background: #d4efdf; color: #1a5e2c; }
#reff-result.turbulent  { background: #fadbd8; color: #922b21; }
#reff-result.critical   { background: #fef9e7; color: #7d6608; }

@media (prefers-color-scheme: dark) {
  #reff-result.damped    { background: #1a3d2b; color: #6fcf97; }
  #reff-result.turbulent { background: #3d1a1a; color: #eb5757; }
  #reff-result.critical  { background: #3d350a; color: #f2c94c; }
}

/* ── Contribution blocks ─────────────────────────────────────────────────── */
.contrib-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 20px;
  margin-top: 20px;
}

.contrib-card {
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
}

.contrib-card .label {
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-2);
  margin-bottom: 6px;
}

/* ── Hypotheses table ────────────────────────────────────────────────────── */
.hyp-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 16px;
  font-size: 0.9rem;
}

.hyp-table th, .hyp-table td {
  padding: 10px 12px;
  border: 1px solid var(--border);
  text-align: left;
  vertical-align: top;
}

.hyp-table th {
  background: var(--bg-alt);
  font-weight: 600;
}

.hyp-table td:first-child {
  font-weight: 700;
  white-space: nowrap;
  color: var(--accent);
}

/* ── Code blocks ─────────────────────────────────────────────────────────── */
pre {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 20px;
  overflow-x: auto;
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  font-size: 0.875rem;
  line-height: 1.55;
  margin: 14px 0;
}

code {
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  font-size: 0.875em;
  background: var(--code-bg);
  padding: 2px 5px;
  border-radius: 3px;
}

pre code { background: none; padding: 0; font-size: inherit; }

.copy-btn {
  float: right;
  font-size: 0.78rem;
  padding: 4px 10px;
  margin-left: 8px;
  margin-top: -2px;
  border-radius: 4px;
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--text-muted);
  cursor: pointer;
}

.copy-btn:hover { color: var(--text); }

/* ── Footer ──────────────────────────────────────────────────────────────── */
footer {
  border-top: 1px solid var(--border);
  padding: 32px 0;
  color: var(--text-muted);
  font-size: 0.875rem;
}

footer a { color: var(--text-muted); }
.footer-row { display: flex; flex-wrap: wrap; gap: 16px; justify-content: space-between; }

/* ── Responsive ──────────────────────────────────────────────────────────── */
@media (max-width: 600px) {
  .masthead-inner { flex-direction: column; align-items: center; text-align: center; }
  .cover-img { width: 160px; }
  .masthead-text { text-align: left; }
  .slider-row { grid-template-columns: 90px 1fr 50px; }
  .hyp-table { font-size: 0.82rem; }
  .button-row { flex-direction: column; }
}