/* ============================================================
   base.css — design tokens, reset, typography, shared elements
   ============================================================ */

:root {
  color-scheme: light;

  /* surfaces */
  --bg: #faf7f1;
  --bg-elev: #fffdf9;
  --bg-sunken: #f3eee3;

  /* text */
  --text: #26262c;
  --text-soft: #5d5d68;
  --text-faint: #8b8b96;

  /* lines */
  --border: #e6dfd1;
  --border-strong: #cfc5b1;

  /* bitcoin accent */
  --accent: #f7931a;
  --accent-deep: #c96a05;
  --accent-soft: rgba(247, 147, 26, 0.14);
  --accent-glow: rgba(247, 147, 26, 0.30);

  /* annotation palettes */
  --note-info-bg: #eef3f9;
  --note-info-border: #c2d4e9;
  --note-why-bg: #edf7ef;
  --note-why-border: #bcdec7;
  --note-warn-bg: #fdf3e2;
  --note-warn-border: #efd09e;
  --disc-bg: #eef3ff;
  --disc-border: #b7cbf2;

  /* semantic */
  --ok: #2e8b57;
  --err: #c3272f;

  /* chrome */
  --header-bg: rgba(250, 247, 241, 0.9);
  --shadow: 0 10px 30px rgba(60, 50, 30, 0.10);

  /* typography */
  --font-serif: Georgia, "Iowan Old Style", "Times New Roman", serif;
  --font-sans: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --font-mono: ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas, monospace;

  --radius: 12px;
  --header-h: 64px;
}

html[data-theme="dark"] {
  color-scheme: dark;

  --bg: #17181c;
  --bg-elev: #1e2026;
  --bg-sunken: #121316;

  --text: #e8e6df;
  --text-soft: #a9aab4;
  --text-faint: #7d7d87;

  --border: #333640;
  --border-strong: #474c59;

  --accent: #f7a14a;
  --accent-deep: #ffb668;
  --accent-soft: rgba(247, 161, 74, 0.16);
  --accent-glow: rgba(247, 161, 74, 0.36);

  --note-info-bg: #1c2430;
  --note-info-border: #33516e;
  --note-why-bg: #14251b;
  --note-why-border: #2d6c46;
  --note-warn-bg: #2b2112;
  --note-warn-border: #8d6d2e;
  --disc-bg: #16203a;
  --disc-border: #3d5c9e;

  --ok: #6fce97;
  --err: #f07d83;

  --header-bg: rgba(23, 24, 28, 0.92);
  --shadow: 0 14px 34px rgba(0, 0, 0, 0.5);
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

::selection {
  background: var(--accent-soft);
}

a {
  color: var(--accent-deep);
  text-decoration-thickness: 1px;
  text-underline-offset: 2px;
}

a:hover {
  color: var(--accent);
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 100;
  background: var(--bg-elev);
  border: 1px solid var(--border-strong);
  border-radius: 8px;
  padding: 8px 12px;
}

.skip-link:focus {
  left: 8px;
  top: 8px;
}

/* ============ header & progress ============ */

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: var(--header-bg);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}

.progress {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: transparent;
}

#progress-bar {
  display: block;
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, var(--accent), var(--accent-deep));
}

.header-inner {
  max-width: 1240px;
  margin: 0 auto;
  padding: 0 24px;
  height: var(--header-h);
  display: flex;
  align-items: center;
  gap: 24px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-weight: 700;
  color: var(--text);
  text-decoration: none;
  letter-spacing: -0.01em;
  white-space: nowrap;
}

.brand-mark {
  display: inline-grid;
  place-items: center;
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--accent);
  color: #fff;
  font-weight: 800;
  font-size: 15px;
}

.brand-tag {
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-faint);
  border: 1px solid var(--border-strong);
  border-radius: 999px;
  padding: 2px 8px;
}

.section-nav {
  display: flex;
  gap: 4px;
  margin-left: auto;
}

.section-nav a {
  text-decoration: none;
  color: var(--text-soft);
  font-size: 14px;
  font-weight: 600;
  padding: 7px 12px;
  border-radius: 999px;
  border: 1px solid transparent;
  transition: color 0.15s, background 0.15s, border-color 0.15s;
}

.section-nav a:hover {
  color: var(--text);
  background: var(--accent-soft);
}

.section-nav a.active {
  color: var(--accent-deep);
  border-color: var(--accent);
  background: var(--accent-soft);
}

.header-actions {
  display: flex;
  gap: 8px;
  margin-left: 8px;
}

.header-actions button,
#focus-btn,
#theme-btn {
  font: inherit;
  font-size: 13px;
  font-weight: 600;
  color: var(--text-soft);
  background: transparent;
  border: 1px solid var(--border-strong);
  border-radius: 999px;
  padding: 7px 12px;
  cursor: pointer;
  transition: color 0.15s, border-color 0.15s, background 0.15s;
}

.header-actions button:hover,
#focus-btn:hover,
#theme-btn:hover {
  color: var(--text);
  background: var(--accent-soft);
  border-color: var(--accent);
}

.header-actions button[aria-pressed="true"] {
  color: var(--accent-deep);
  border-color: var(--accent);
  background: var(--accent-soft);
}