/* ═══════════════════════════════════════════════════════════
   AI Training Platform — design system
   ═══════════════════════════════════════════════════════════ */

:root {
  --bg:            #0d1017;
  --bg-raised:     #141922;
  --bg-card:       #171d28;
  --bg-inset:      #10151d;
  --border:        #252d3b;
  --border-soft:   #1e2531;

  --text:          #e6ebf3;
  --text-dim:      #9aa6b8;
  --text-faint:    #6b7688;

  --accent:        #6d8cff;
  --accent-soft:   #2a3760;
  --accent-glow:   rgba(109, 140, 255, 0.14);

  --claude:        #d97757;
  --claude-soft:   #40261d;
  --openai:        #3fbf8f;
  --openai-soft:   #17372c;

  --warn:          #e0b341;
  --danger:        #e06c75;
  --ok:            #3fbf8f;

  --mono: ui-monospace, "SF Mono", "Cascadia Code", "JetBrains Mono", Menlo, Consolas, monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, "Helvetica Neue", Arial, sans-serif;

  --radius:    12px;
  --radius-sm: 8px;
  --maxw:      1180px;
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }

body {
  font-family: var(--sans);
  background: var(--bg);
  color: var(--text);
  font-size: 16px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

body::before {
  content: "";
  position: fixed; inset: 0;
  background:
    radial-gradient(900px 500px at 12% -8%, rgba(109,140,255,0.10), transparent 60%),
    radial-gradient(800px 460px at 92% 4%, rgba(217,119,87,0.07), transparent 60%);
  pointer-events: none;
  z-index: 0;
}

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

::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: #2b3444; border-radius: 5px; border: 2px solid var(--bg); }
::-webkit-scrollbar-thumb:hover { background: #3a4557; }

/* ── Layout ───────────────────────────────────────────────── */

.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; position: relative; z-index: 1; }
.wrap-narrow { max-width: 860px; margin: 0 auto; padding: 0 24px; position: relative; z-index: 1; }

section { padding: 56px 0; }
section.tight { padding: 32px 0; }

/* ── Header / nav ─────────────────────────────────────────── */

.site-header {
  position: sticky; top: 0; z-index: 100;
  background: rgba(13, 16, 23, 0.86);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border-soft);
}
.nav-inner {
  max-width: var(--maxw); margin: 0 auto; padding: 0 24px;
  height: 62px; display: flex; align-items: center; justify-content: space-between; gap: 20px;
}
.brand {
  display: flex; align-items: center; gap: 10px;
  font-weight: 650; font-size: 15px; letter-spacing: -0.2px;
  color: var(--text); text-decoration: none; white-space: nowrap;
}
.brand:hover { text-decoration: none; }
.brand-mark {
  width: 28px; height: 28px; border-radius: 8px; flex-shrink: 0;
  background: linear-gradient(135deg, var(--accent), var(--claude));
  display: grid; place-items: center;
  font-size: 13px; font-weight: 800; color: #0d1017;
}
.brand small { color: var(--text-faint); font-weight: 500; font-size: 11px; display: block; line-height: 1; margin-top: 2px; }

.main-nav { display: flex; align-items: center; gap: 4px; }
.main-nav a {
  font-size: 13.5px; font-weight: 500; color: var(--text-dim);
  padding: 7px 12px; border-radius: var(--radius-sm); text-decoration: none;
  transition: background 0.15s, color 0.15s;
}
.main-nav a:hover { background: var(--bg-card); color: var(--text); text-decoration: none; }
.main-nav a.active { color: var(--text); background: var(--bg-card); }

/* Back to the main site. Visually separated from the in-site nav so it does
   not read as one more section of the training platform. */
.main-nav a.nav-back {
  color: var(--text-faint); font-size: 12.5px;
  margin-left: 6px; padding-left: 14px;
  border-left: 1px solid var(--border);
  border-radius: 0;
}
.main-nav a.nav-back:hover { color: var(--text-dim); background: none; }

.hamburger {
  display: none; flex-direction: column; gap: 4px; cursor: pointer;
  background: none; border: none; padding: 8px;
}
.hamburger span { width: 20px; height: 2px; background: var(--text-dim); border-radius: 2px; }

/* ── Hero ─────────────────────────────────────────────────── */

.hero { padding: 76px 0 44px; }
.eyebrow {
  display: inline-flex; align-items: center; gap: 8px;
  font-size: 11.5px; font-weight: 600; letter-spacing: 1.4px; text-transform: uppercase;
  color: var(--accent); background: var(--accent-glow);
  border: 1px solid var(--accent-soft); border-radius: 100px; padding: 5px 13px;
  margin-bottom: 20px;
}
h1 {
  font-size: clamp(30px, 5.2vw, 50px); line-height: 1.12; font-weight: 700;
  letter-spacing: -1.4px; margin-bottom: 18px; max-width: 17ch;
}
.hero .lede { font-size: 17.5px; color: var(--text-dim); max-width: 62ch; margin-bottom: 30px; }

/* ── Buttons ──────────────────────────────────────────────── */

.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 11px 20px; border-radius: var(--radius-sm);
  font-size: 14px; font-weight: 600; cursor: pointer;
  border: 1px solid transparent; text-decoration: none;
  transition: all 0.15s; font-family: inherit;
}
.btn:hover { text-decoration: none; }
.btn-primary { background: var(--accent); color: #0b0e14; }
.btn-primary:hover { background: #829eff; transform: translateY(-1px); }
.btn-ghost { background: var(--bg-card); color: var(--text); border-color: var(--border); }
.btn-ghost:hover { border-color: #3a4557; background: var(--bg-raised); }
.btn-sm { padding: 7px 14px; font-size: 13px; }
.btn:disabled { opacity: 0.4; cursor: not-allowed; transform: none; }

.btn-row { display: flex; gap: 12px; flex-wrap: wrap; }

/* ── Cards & grids ────────────────────────────────────────── */

.grid { display: grid; gap: 18px; }
.grid-2 { grid-template-columns: repeat(2, 1fr); }
.grid-3 { grid-template-columns: repeat(3, 1fr); }
.grid-4 { grid-template-columns: repeat(4, 1fr); }

.card {
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 22px;
  transition: border-color 0.18s, transform 0.18s;
}
.card:hover { border-color: #33405a; }
a.card:hover { text-decoration: none; transform: translateY(-2px); }

.card h3 { font-size: 16.5px; font-weight: 650; margin-bottom: 8px; letter-spacing: -0.2px; }
.card p { font-size: 14px; color: var(--text-dim); }

/* Track cards */
.track-card { position: relative; overflow: hidden; display: block; color: inherit; padding: 26px; }
.track-card::before {
  content: ""; position: absolute; top: 0; left: 0; right: 0; height: 3px;
}
.track-card.claude::before { background: linear-gradient(90deg, var(--claude), #f0a882); }
.track-card.openai::before { background: linear-gradient(90deg, var(--openai), #7fe0bd); }

.track-head { display: flex; align-items: center; gap: 12px; margin-bottom: 14px; }
.track-logo {
  width: 38px; height: 38px; border-radius: 10px; flex-shrink: 0;
  display: grid; place-items: center; font-weight: 800; font-size: 15px;
}
.track-card.claude .track-logo { background: var(--claude-soft); color: var(--claude); }
.track-card.openai .track-logo { background: var(--openai-soft); color: var(--openai); }
.track-head h3 { margin: 0; font-size: 19px; }
.track-head .sub { font-size: 12.5px; color: var(--text-faint); }

.track-levels { list-style: none; margin: 16px 0; display: grid; gap: 7px; }
.track-levels li {
  font-size: 13.5px; color: var(--text-dim);
  display: flex; align-items: center; gap: 9px;
}
.track-levels li::before {
  content: ""; width: 5px; height: 5px; border-radius: 50%;
  background: var(--text-faint); flex-shrink: 0;
}

/* ── Progress ─────────────────────────────────────────────── */

.progress-bar {
  height: 6px; background: var(--bg-inset); border-radius: 3px; overflow: hidden;
  border: 1px solid var(--border-soft);
}
.progress-bar span { display: block; height: 100%; border-radius: 3px; transition: width 0.5s ease; }
.track-card.claude .progress-bar span { background: var(--claude); }
.track-card.openai .progress-bar span { background: var(--openai); }
.progress-bar span { background: var(--accent); }

.progress-meta {
  display: flex; justify-content: space-between; align-items: center;
  font-size: 12.5px; color: var(--text-faint); margin-top: 8px;
}

/* ── Stats ────────────────────────────────────────────────── */

.stat { text-align: center; padding: 18px 12px; }
.stat .num {
  font-size: 30px; font-weight: 700; letter-spacing: -1px;
  font-variant-numeric: tabular-nums; line-height: 1.1;
}
.stat .lbl { font-size: 11.5px; color: var(--text-faint); text-transform: uppercase; letter-spacing: 1px; margin-top: 5px; }

/* ── Section headings ─────────────────────────────────────── */

.sec-head { margin-bottom: 26px; }
.sec-head h2 {
  font-size: clamp(22px, 3.2vw, 29px); font-weight: 680; letter-spacing: -0.8px; margin-bottom: 8px;
}
.sec-head p { color: var(--text-dim); font-size: 15px; max-width: 66ch; }

/* ── Curriculum page ──────────────────────────────────────── */

.level-block { margin-bottom: 14px; }

.level-head {
  display: flex; align-items: center; gap: 14px; width: 100%;
  padding: 18px 20px; cursor: pointer; text-align: left;
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius); color: inherit; font-family: inherit;
  transition: border-color 0.15s;
}
.level-head:hover { border-color: #33405a; }
.level-head[aria-expanded="true"] { border-radius: var(--radius) var(--radius) 0 0; border-bottom-color: transparent; }

.level-badge {
  width: 34px; height: 34px; border-radius: 9px; flex-shrink: 0;
  display: grid; place-items: center; font-size: 13px; font-weight: 700;
  background: var(--accent-soft); color: var(--accent);
}
.level-title { flex: 1; min-width: 0; }
.level-title strong { display: block; font-size: 16px; font-weight: 640; letter-spacing: -0.2px; }
.level-title span { font-size: 13px; color: var(--text-faint); }
.level-count { font-size: 12.5px; color: var(--text-faint); white-space: nowrap; font-variant-numeric: tabular-nums; }
.chev { color: var(--text-faint); transition: transform 0.2s; flex-shrink: 0; font-size: 12px; }
.level-head[aria-expanded="true"] .chev { transform: rotate(90deg); }

.lesson-list {
  border: 1px solid var(--border); border-top: none;
  border-radius: 0 0 var(--radius) var(--radius);
  background: var(--bg-raised); overflow: hidden;
}
.lesson-list[hidden] { display: none; }

.lesson-row {
  display: flex; align-items: center; gap: 14px;
  padding: 13px 20px; border-top: 1px solid var(--border-soft);
  cursor: pointer; transition: background 0.13s;
}
.lesson-row:first-child { border-top: none; }
.lesson-row:hover { background: var(--bg-card); }

.tick {
  width: 20px; height: 20px; border-radius: 50%; flex-shrink: 0;
  border: 1.5px solid var(--border); display: grid; place-items: center;
  font-size: 11px; color: transparent; transition: all 0.18s;
}
.lesson-row.done .tick { background: var(--ok); border-color: var(--ok); color: #0b0e14; }
.lesson-row.done .lesson-name { color: var(--text-faint); }

.lesson-name { flex: 1; font-size: 14.5px; min-width: 0; }
.lesson-mins { font-size: 12px; color: var(--text-faint); white-space: nowrap; }

/* ── Lesson viewer (modal) ────────────────────────────────── */

.viewer {
  position: fixed; inset: 0; z-index: 300;
  background: rgba(6, 8, 12, 0.78); backdrop-filter: blur(5px);
  display: none; padding: 28px 20px; overflow-y: auto;
}
.viewer.open { display: block; }

.viewer-panel {
  max-width: 820px; margin: 0 auto;
  background: var(--bg-raised); border: 1px solid var(--border);
  border-radius: 14px; overflow: hidden;
  animation: rise 0.24s ease;
}
@keyframes rise { from { opacity: 0; transform: translateY(14px); } to { opacity: 1; transform: none; } }

.viewer-top {
  position: sticky; top: 0; z-index: 2;
  display: flex; align-items: flex-start; gap: 16px;
  padding: 20px 26px; background: var(--bg-raised);
  border-bottom: 1px solid var(--border-soft);
}
.viewer-top .meta { flex: 1; min-width: 0; }
.viewer-top .kicker {
  font-size: 11px; font-weight: 600; letter-spacing: 1.2px; text-transform: uppercase;
  color: var(--accent); margin-bottom: 5px;
}
.viewer-top h2 { font-size: 21px; font-weight: 660; letter-spacing: -0.4px; line-height: 1.3; }
.viewer-close {
  background: var(--bg-card); border: 1px solid var(--border); color: var(--text-dim);
  width: 32px; height: 32px; border-radius: 8px; cursor: pointer;
  font-size: 16px; line-height: 1; flex-shrink: 0;
}
.viewer-close:hover { color: var(--text); border-color: #3a4557; }

.viewer-body { padding: 26px; }

/* Lesson content typography */
.lesson-content > * + * { margin-top: 15px; }
.lesson-content p { font-size: 15px; color: #c9d3e2; }
.lesson-content h4 {
  font-size: 14px; font-weight: 650; letter-spacing: 0.2px;
  margin-top: 26px; color: var(--text);
}
.lesson-content ul, .lesson-content ol { padding-left: 22px; }
.lesson-content li { font-size: 14.5px; color: #c9d3e2; margin-bottom: 7px; }
.lesson-content strong { color: var(--text); font-weight: 640; }
.lesson-content code {
  font-family: var(--mono); font-size: 12.8px;
  background: var(--bg-inset); border: 1px solid var(--border-soft);
  padding: 1.5px 5px; border-radius: 5px; color: #a5c8ff;
}
.lesson-content pre {
  background: var(--bg-inset); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 15px 17px;
  overflow-x: auto; font-family: var(--mono); font-size: 12.8px; line-height: 1.62;
}
.lesson-content pre code { background: none; border: none; padding: 0; color: #cbd6e8; }
.lesson-content table { width: 100%; border-collapse: collapse; font-size: 13.5px; }
.lesson-content th, .lesson-content td {
  text-align: left; padding: 9px 12px; border-bottom: 1px solid var(--border-soft);
}
.lesson-content th { color: var(--text-faint); font-weight: 600; font-size: 11.5px; text-transform: uppercase; letter-spacing: 0.7px; }
.lesson-content td { color: #c9d3e2; }
.lesson-content td code { font-size: 12.2px; }
.table-scroll { overflow-x: auto; }

.callout {
  border-left: 3px solid var(--accent); background: var(--accent-glow);
  padding: 13px 16px; border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
  font-size: 14px; color: #c9d3e2;
}
.callout.warn { border-left-color: var(--warn); background: rgba(224, 179, 65, 0.09); }
.callout.danger { border-left-color: var(--danger); background: rgba(224, 108, 117, 0.09); }
.callout strong { color: var(--text); }

/* Takeaways / exercise blocks */
.block {
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--bg-card); padding: 18px 20px; margin-top: 24px;
}
.block > h4 {
  font-size: 11.5px; letter-spacing: 1.2px; text-transform: uppercase;
  color: var(--text-faint); font-weight: 650; margin: 0 0 12px;
}
.block ul { padding-left: 20px; margin: 0; }
.block li { font-size: 14px; color: #c9d3e2; margin-bottom: 6px; }
.block p { font-size: 14px; color: #c9d3e2; }
.block > * + p, .block > * + pre { margin-top: 12px; }

/* ── Quiz ─────────────────────────────────────────────────── */

.quiz { margin-top: 26px; border-top: 1px solid var(--border-soft); padding-top: 24px; }
.quiz > h4 {
  font-size: 11.5px; letter-spacing: 1.2px; text-transform: uppercase;
  color: var(--text-faint); font-weight: 650; margin-bottom: 16px;
}
.q { margin-bottom: 20px; }
.q-text { font-size: 14.5px; font-weight: 560; margin-bottom: 10px; }
.opts { display: grid; gap: 7px; }
.opt {
  display: flex; align-items: flex-start; gap: 10px;
  padding: 10px 13px; border: 1px solid var(--border); border-radius: var(--radius-sm);
  background: var(--bg-inset); cursor: pointer; font-size: 14px; color: #c9d3e2;
  transition: all 0.14s; text-align: left; font-family: inherit; width: 100%;
}
.opt:hover:not(:disabled) { border-color: #3a4557; }
.opt.picked { border-color: var(--accent); background: var(--accent-glow); }
.opt.right { border-color: var(--ok); background: rgba(63,191,143,0.11); }
.opt.wrong { border-color: var(--danger); background: rgba(224,108,117,0.11); }
.opt .mark { flex-shrink: 0; width: 16px; font-weight: 700; font-size: 12px; }
.opt:disabled { cursor: default; }

.explain {
  margin-top: 9px; font-size: 13.5px; color: var(--text-dim);
  padding: 10px 13px; background: var(--bg-inset);
  border-radius: var(--radius-sm); border: 1px solid var(--border-soft);
}
.explain[hidden] { display: none; }

.quiz-foot {
  display: flex; align-items: center; justify-content: space-between; gap: 14px;
  flex-wrap: wrap; margin-top: 20px; padding-top: 18px; border-top: 1px solid var(--border-soft);
}
.score { font-size: 14px; font-weight: 600; }
.score.pass { color: var(--ok); }
.score.fail { color: var(--warn); }

/* ── News page ────────────────────────────────────────────── */

.news-item {
  display: block; padding: 17px 20px; border: 1px solid var(--border);
  border-radius: var(--radius); background: var(--bg-card);
  color: inherit; margin-bottom: 11px; transition: border-color 0.15s, transform 0.15s;
}
.news-item:hover { text-decoration: none; border-color: #33405a; transform: translateX(2px); }
.news-meta { display: flex; align-items: center; gap: 9px; margin-bottom: 7px; flex-wrap: wrap; }
.news-item h3 { font-size: 15.5px; font-weight: 620; line-height: 1.4; letter-spacing: -0.2px; }
.news-item p { font-size: 13.5px; color: var(--text-dim); margin-top: 6px; }

.pill {
  font-size: 10.5px; font-weight: 650; letter-spacing: 0.7px; text-transform: uppercase;
  padding: 3px 9px; border-radius: 100px; white-space: nowrap;
}
.pill.anthropic { background: var(--claude-soft); color: var(--claude); }
.pill.openai    { background: var(--openai-soft); color: var(--openai); }
.pill.industry  { background: #2b2440; color: #b49ae8; }
.pill.date      { background: var(--bg-inset); color: var(--text-faint); border: 1px solid var(--border-soft); }

.feed-status {
  font-size: 13px; color: var(--text-faint); padding: 14px 18px;
  border: 1px dashed var(--border); border-radius: var(--radius); margin-bottom: 14px;
}

.filter-row { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 20px; }
.chip {
  padding: 6px 14px; border-radius: 100px; font-size: 13px; font-weight: 550;
  background: var(--bg-card); border: 1px solid var(--border); color: var(--text-dim);
  cursor: pointer; font-family: inherit; transition: all 0.14s;
}
.chip:hover { border-color: #3a4557; color: var(--text); }
.chip.on { background: var(--accent); border-color: var(--accent); color: #0b0e14; }

/* ── Labs ─────────────────────────────────────────────────── */

.lab {
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--bg-card); margin-bottom: 14px; overflow: hidden;
}
.lab-head {
  display: flex; align-items: center; gap: 14px; padding: 17px 20px;
  cursor: pointer; width: 100%; background: none; border: none;
  color: inherit; font-family: inherit; text-align: left;
}
.lab-head:hover { background: var(--bg-raised); }
.lab-head .lab-title { flex: 1; font-size: 15.5px; font-weight: 600; letter-spacing: -0.2px; }
.lab-body { padding: 0 20px 20px; border-top: 1px solid var(--border-soft); }
.lab-body[hidden] { display: none; }
.lab-body > * + * { margin-top: 14px; }
.lab-body p { font-size: 14.5px; color: #c9d3e2; }
.lab-body h4 { font-size: 13px; letter-spacing: 0.6px; text-transform: uppercase; color: var(--text-faint); margin-top: 20px; }
.lab-body ol, .lab-body ul { padding-left: 22px; }
.lab-body li { font-size: 14.5px; color: #c9d3e2; margin-bottom: 6px; }
.lab-body pre {
  background: var(--bg-inset); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 15px 17px; overflow-x: auto;
  font-family: var(--mono); font-size: 12.8px; line-height: 1.62; color: #cbd6e8;
}
.lab-body code {
  font-family: var(--mono); font-size: 12.8px; background: var(--bg-inset);
  border: 1px solid var(--border-soft); padding: 1.5px 5px; border-radius: 5px; color: #a5c8ff;
}
.lab-body pre code { background: none; border: none; padding: 0; }

.tag {
  display: inline-block; font-size: 10.5px; font-weight: 650; letter-spacing: 0.7px;
  text-transform: uppercase; padding: 3px 9px; border-radius: 100px;
  background: var(--bg-inset); border: 1px solid var(--border); color: var(--text-faint);
}
.tag.claude { background: var(--claude-soft); border-color: transparent; color: var(--claude); }
.tag.openai { background: var(--openai-soft); border-color: transparent; color: var(--openai); }
.tag.both   { background: var(--accent-soft); border-color: transparent; color: var(--accent); }

.copy-btn {
  font-size: 11.5px; padding: 4px 10px; border-radius: 6px; cursor: pointer;
  background: var(--bg-card); border: 1px solid var(--border); color: var(--text-dim);
  font-family: inherit;
}
.copy-btn:hover { color: var(--text); border-color: #3a4557; }
.pre-wrap { position: relative; }
.pre-wrap .copy-btn { position: absolute; top: 9px; right: 9px; }

/* ── Glossary ─────────────────────────────────────────────── */

.gloss-item {
  padding: 16px 0; border-bottom: 1px solid var(--border-soft);
}
.gloss-item dt { font-size: 15px; font-weight: 640; margin-bottom: 5px; letter-spacing: -0.2px; }
.gloss-item dd { font-size: 14.5px; color: var(--text-dim); }
.gloss-item dd code { font-family: var(--mono); font-size: 12.6px; background: var(--bg-inset); padding: 1.5px 5px; border-radius: 5px; color: #a5c8ff; }

.search-box {
  width: 100%; padding: 11px 16px; font-size: 15px; font-family: inherit;
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius-sm); color: var(--text); margin-bottom: 22px;
}
.search-box:focus { outline: none; border-color: var(--accent); }
.search-box::placeholder { color: var(--text-faint); }

/* ── Footer ───────────────────────────────────────────────── */

.site-footer {
  border-top: 1px solid var(--border-soft); margin-top: 50px;
  padding: 30px 0; font-size: 13px; color: var(--text-faint);
}
.footer-inner {
  max-width: var(--maxw); margin: 0 auto; padding: 0 24px;
  display: flex; justify-content: space-between; align-items: center; gap: 18px; flex-wrap: wrap;
}
.site-footer a { color: var(--text-dim); }

/* ── Utilities ────────────────────────────────────────────── */

.muted { color: var(--text-dim); }
.faint { color: var(--text-faint); }
.small { font-size: 13px; }
.center { text-align: center; }
.mt-0 { margin-top: 0; }
.mt-1 { margin-top: 10px; }
.mt-2 { margin-top: 20px; }
.mt-3 { margin-top: 32px; }
.mb-2 { margin-bottom: 20px; }
.nowrap { white-space: nowrap; }

/* ── Responsive ───────────────────────────────────────────── */

@media (max-width: 900px) {
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
}

@media (max-width: 720px) {
  .main-nav {
    display: none; position: absolute; top: 62px; left: 0; right: 0;
    flex-direction: column; align-items: stretch; gap: 2px;
    background: var(--bg-raised); border-bottom: 1px solid var(--border);
    padding: 10px 16px 16px;
  }
  .main-nav.open { display: flex; }
  .main-nav a.nav-back {
    border-left: none; border-top: 1px solid var(--border);
    margin-left: 0; padding-left: 12px; margin-top: 6px; padding-top: 12px;
  }
  .hamburger { display: flex; }
  .grid-2, .grid-3 { grid-template-columns: 1fr; }
  .hero { padding: 48px 0 32px; }
  section { padding: 40px 0; }
  .viewer { padding: 0; }
  .viewer-panel { border-radius: 0; min-height: 100vh; border: none; }
  .viewer-body { padding: 20px; }
  .viewer-top { padding: 16px 20px; }
  .wrap, .wrap-narrow, .nav-inner, .footer-inner { padding-left: 18px; padding-right: 18px; }
}

@media (max-width: 460px) {
  .grid-4 { grid-template-columns: 1fr; }
  .brand small { display: none; }
}

/* ── Light theme (respects OS preference) ─────────────────── */

@media (prefers-color-scheme: light) {
  :root {
    --bg: #f7f8fb;
    --bg-raised: #ffffff;
    --bg-card: #ffffff;
    --bg-inset: #f1f3f8;
    --border: #dfe3ec;
    --border-soft: #e9ecf3;
    --text: #131722;
    --text-dim: #4d5768;
    --text-faint: #7d8698;
    --accent: #3d5ce0;
    --accent-soft: #d6ddfa;
    --accent-glow: rgba(61, 92, 224, 0.07);
    --claude-soft: #fbe7de;
    --openai-soft: #d9f4e9;
  }
  body::before {
    background:
      radial-gradient(900px 500px at 12% -8%, rgba(61,92,224,0.07), transparent 60%),
      radial-gradient(800px 460px at 92% 4%, rgba(217,119,87,0.06), transparent 60%);
  }
  .site-header { background: rgba(247, 248, 251, 0.9); }
  .brand-mark { color: #fff; }
  .btn-primary { color: #fff; }
  .lesson-content p, .lesson-content li, .lesson-content td,
  .block li, .block p, .lab-body p, .lab-body li, .opt, .callout { color: #384254; }
  .lesson-content pre code, .lab-body pre { color: #2b3444; }
  .lesson-content code, .lab-body code, .gloss-item dd code { color: #2f4bbd; }
  .tick { border-color: #cbd2e0; }
  ::-webkit-scrollbar-thumb { background: #ccd3e0; }
}