:root {
  color-scheme: dark;
  --bg: #08111f;
  --bg-2: #0d1830;
  --panel: rgba(255,255,255,0.075);
  --panel-strong: rgba(255,255,255,0.12);
  --line: rgba(255,255,255,0.14);
  --text: #f6f8ff;
  --muted: #aeb9cf;
  --soft: #d7def2;
  --accent: #68e1fd;
  --accent-2: #9b7cff;
  --accent-3: #f7c948;
  --good: #5ff0a5;
  --warn: #ffcf70;
  --bad: #ff7b8a;
  --shadow: 0 24px 80px rgba(0,0,0,0.35);
  --radius: 22px;
  --radius-sm: 14px;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(circle at 15% 4%, rgba(104,225,253,0.22), transparent 32rem),
    radial-gradient(circle at 85% 10%, rgba(155,124,255,0.19), transparent 28rem),
    linear-gradient(180deg, #070c17 0%, var(--bg) 44%, #0a1020 100%);
  color: var(--text);
}

a { color: inherit; }
button, input, textarea, select { font: inherit; }
button { cursor: pointer; }

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  display: grid;
  grid-template-columns: auto minmax(0, 1fr) auto;
  gap: 1rem;
  align-items: center;
  padding: 0.8rem clamp(1rem, 3vw, 2rem);
  background: rgba(7, 12, 23, 0.78);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(18px);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.75rem;
  text-decoration: none;
  min-width: max-content;
}
.brand-mark {
  width: 42px;
  height: 42px;
  display: grid;
  place-items: center;
  border-radius: 14px;
  color: #06101d;
  background: linear-gradient(135deg, var(--accent), var(--accent-3));
  font-weight: 950;
  box-shadow: 0 10px 28px rgba(104,225,253,0.25);
}
.brand strong, .brand small { display: block; line-height: 1.05; }
.brand small { color: var(--muted); font-size: 0.78rem; margin-top: 0.15rem; }

.tabs {
  display: flex;
  justify-content: center;
  gap: 0.35rem;
  flex-wrap: wrap;
}
.tab, .pill {
  border: 1px solid transparent;
  border-radius: 999px;
  background: transparent;
  color: var(--muted);
  padding: 0.58rem 0.85rem;
  font-weight: 800;
  font-size: 0.88rem;
}
.tab:hover, .pill:hover { color: var(--text); background: rgba(255,255,255,0.07); }
.tab.is-active, .pill.is-active {
  color: #06101d;
  background: linear-gradient(135deg, var(--accent), #b0f3ff);
  box-shadow: 0 10px 28px rgba(104,225,253,0.18);
}
.workspace-link {
  justify-self: end;
  padding: 0.62rem 0.85rem;
  border-radius: 999px;
  border: 1px solid var(--line);
  color: var(--soft);
  text-decoration: none;
  font-weight: 800;
  font-size: 0.85rem;
  white-space: nowrap;
}
.workspace-link:hover { border-color: rgba(104,225,253,0.55); background: rgba(104,225,253,0.1); }

main { min-height: calc(100vh - 150px); }
.page { display: none; animation: pageIn 180ms ease-out; }
.page.is-active { display: block; }
@keyframes pageIn { from { opacity: 0; transform: translateY(8px); } to { opacity: 1; transform: translateY(0); } }

.section-shell {
  width: min(1180px, calc(100% - 2rem));
  margin: 0 auto;
  padding: clamp(2.1rem, 5vw, 4.5rem) 0;
}
.section-heading { max-width: 780px; margin-bottom: 1.5rem; }
.section-heading.narrow { max-width: 820px; }
.eyebrow {
  color: var(--accent);
  font-size: 0.78rem;
  font-weight: 950;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  margin: 0 0 0.65rem;
}
h1, h2, h3 { margin: 0; letter-spacing: -0.035em; }
h1 { font-size: clamp(2.3rem, 7vw, 5.8rem); line-height: 0.94; }
h2 { font-size: clamp(1.45rem, 3.2vw, 2.45rem); line-height: 1.05; }
h3 { font-size: 1.08rem; }
p { color: var(--muted); line-height: 1.68; }

.hero {
  display: grid;
  grid-template-columns: minmax(0, 1.08fr) minmax(310px, 0.62fr);
  gap: clamp(1.5rem, 4vw, 3rem);
  align-items: center;
  min-height: 72vh;
}
.hero-text { font-size: clamp(1.06rem, 2.4vw, 1.35rem); max-width: 760px; color: var(--soft); }
.hero-actions { display: flex; gap: 0.85rem; flex-wrap: wrap; margin-top: 1.4rem; }
.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--line);
  border-radius: 999px;
  min-height: 44px;
  padding: 0.75rem 1.08rem;
  color: var(--text);
  text-decoration: none;
  font-weight: 900;
  transition: transform 160ms ease, border-color 160ms ease, background 160ms ease;
}
.button:hover { transform: translateY(-1px); border-color: rgba(104,225,253,0.6); }
.button.primary { border: 0; color: #06101d; background: linear-gradient(135deg, var(--accent), #b7f5ff); }
.button.ghost { background: rgba(255,255,255,0.07); }
.button.full { width: 100%; }

.hero-card, .card, .course-card, .lab-panel, .leaderboard-card, .glossary-card, .timeline-item {
  border: 1px solid var(--line);
  background: var(--panel);
  box-shadow: var(--shadow);
  backdrop-filter: blur(14px);
}
.hero-card {
  border-radius: 30px;
  padding: 1.5rem;
  position: relative;
  overflow: hidden;
}
.hero-card::before {
  content: "";
  position: absolute;
  inset: -40% -30% auto auto;
  width: 230px;
  height: 230px;
  border-radius: 999px;
  background: rgba(104,225,253,0.22);
  filter: blur(10px);
}
.score-ring {
  position: relative;
  width: 118px;
  height: 118px;
  border-radius: 999px;
  display: grid;
  place-items: center;
  margin-bottom: 1rem;
  background:
    radial-gradient(circle at center, #111d34 58%, transparent 59%),
    conic-gradient(from -90deg, var(--accent), var(--accent-2), var(--accent-3), var(--accent));
}
.score-ring span { display: block; font-size: 2rem; font-weight: 950; }
.score-ring small { display: block; color: var(--muted); text-align: center; margin-top: -1.6rem; }
.stat-row { display: grid; grid-template-columns: 1fr 1fr; gap: 0.85rem; margin-top: 1rem; }
.stat-row span { border: 1px solid var(--line); background: rgba(255,255,255,0.055); border-radius: var(--radius-sm); padding: 0.8rem; }
.stat-row strong, .stat-row small { display: block; }
.stat-row small { color: var(--muted); margin-top: 0.2rem; }

.card-grid, .course-grid, .glossary-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 1rem; }
.card-grid.five { grid-template-columns: repeat(5, minmax(0, 1fr)); }
.card, .glossary-card, .course-card { border-radius: var(--radius); padding: 1rem; }
.card .icon, .course-icon { font-size: 1.55rem; margin-bottom: 0.7rem; }
.card p, .course-card p, .glossary-card p { margin-bottom: 0; font-size: 0.94rem; }

.split { display: grid; grid-template-columns: 0.8fr 1.2fr; gap: 2rem; align-items: start; }
.steps { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 1rem; }
.steps article { border: 1px solid var(--line); background: rgba(255,255,255,0.055); border-radius: var(--radius); padding: 1rem; }
.steps span { width: 34px; height: 34px; display: grid; place-items: center; border-radius: 50%; color: #06101d; background: var(--accent); font-weight: 950; margin-bottom: 0.7rem; }
.steps p { margin-bottom: 0; }
.warning-note { border-top: 1px solid var(--line); display: flex; gap: 0.7rem; color: var(--soft); padding-top: 1.5rem; }
.warning-note strong { color: var(--warn); }

.timeline-controls, .path-filters { display: flex; gap: 0.55rem; flex-wrap: wrap; margin: 1.1rem 0 1.35rem; }
.timeline { position: relative; display: grid; gap: 1rem; }
.timeline::before { content: ""; position: absolute; left: 1.15rem; top: 0; bottom: 0; width: 2px; background: linear-gradient(var(--accent), transparent); opacity: 0.5; }
.timeline-item { position: relative; margin-left: 2.4rem; border-radius: var(--radius); padding: 1rem 1rem 1rem 1.25rem; }
.timeline-item::before { content: ""; position: absolute; left: -2.04rem; top: 1.2rem; width: 12px; height: 12px; border-radius: 999px; background: var(--accent); box-shadow: 0 0 0 6px rgba(104,225,253,0.12); }
.timeline-meta { display: flex; gap: 0.5rem; align-items: center; flex-wrap: wrap; margin-bottom: 0.35rem; }
.year { color: var(--accent-3); font-weight: 950; }
.era { color: #06101d; background: var(--accent); border-radius: 999px; padding: 0.18rem 0.5rem; font-size: 0.75rem; font-weight: 900; }

.course-card { display: flex; flex-direction: column; gap: 0.75rem; }
.course-top { display: flex; justify-content: space-between; gap: 0.75rem; }
.level { width: fit-content; padding: 0.25rem 0.55rem; border-radius: 999px; background: rgba(104,225,253,0.13); color: var(--accent); font-size: 0.76rem; font-weight: 950; }
.course-actions { margin-top: auto; display: flex; gap: 0.55rem; flex-wrap: wrap; }
.mini-button { border: 1px solid var(--line); background: rgba(255,255,255,0.065); color: var(--text); border-radius: 999px; padding: 0.5rem 0.7rem; font-size: 0.83rem; font-weight: 900; }
.mini-button.done { color: #07101e; background: var(--good); border-color: transparent; }

.playground-layout { display: grid; grid-template-columns: minmax(0, 1fr) 390px; gap: 1.25rem; align-items: start; }
.activity-strip { display: grid; grid-template-columns: repeat(4, minmax(0,1fr)); gap: 0.75rem; margin: 1.25rem 0; }
.activity-card { border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 0.85rem; background: rgba(255,255,255,0.06); text-align: left; color: var(--text); }
.activity-card.is-active { border-color: rgba(104,225,253,0.72); background: rgba(104,225,253,0.12); }
.activity-card strong { display: block; margin-bottom: 0.25rem; }
.activity-card small { color: var(--muted); }
.lab-panel { border-radius: var(--radius); padding: 1rem; }
.lab-panel label { display: block; color: var(--soft); font-weight: 900; margin: 0.9rem 0 0.4rem; }
.lab-panel label:first-child { margin-top: 0; }
select, textarea, input {
  width: 100%;
  border: 1px solid var(--line);
  background: rgba(5,10,20,0.65);
  color: var(--text);
  border-radius: var(--radius-sm);
  padding: 0.8rem;
  outline: none;
}
textarea { resize: vertical; min-height: 190px; }
select:focus, textarea:focus, input:focus { border-color: rgba(104,225,253,0.75); box-shadow: 0 0 0 3px rgba(104,225,253,0.12); }
.prompt-tools { display: flex; flex-wrap: wrap; gap: 0.6rem; margin-top: 0.9rem; }
.model-note { display: flex; align-items: center; gap: 0.45rem; color: var(--muted); font-size: 0.88rem; margin-top: 0.8rem; }
.status-dot { width: 10px; height: 10px; border-radius: 999px; background: var(--good); box-shadow: 0 0 0 5px rgba(95,240,165,0.12); }
.status-dot.loading { background: var(--warn); box-shadow: 0 0 0 5px rgba(255,207,112,0.12); }
.status-dot.error { background: var(--bad); box-shadow: 0 0 0 5px rgba(255,123,138,0.12); }
.output-panel { margin-bottom: 1rem; }
.panel-title { display: flex; justify-content: space-between; align-items: center; gap: 0.8rem; margin-bottom: 0.7rem; }
.panel-title button { border: 1px solid var(--line); border-radius: 999px; background: rgba(255,255,255,0.06); color: var(--text); padding: 0.42rem 0.65rem; }
pre#ai-output { white-space: pre-wrap; word-break: break-word; min-height: 260px; margin: 0; color: #eaf2ff; line-height: 1.58; }
.challenge-panel p { margin-top: 0.4rem; }

.leaderboard-layout { display: grid; grid-template-columns: minmax(0, 0.86fr) minmax(340px, 0.64fr); gap: 1.25rem; align-items: start; }
.inline-form { display: flex; gap: 0.65rem; }
.inline-form input { flex: 1; }
.badge-list { display: flex; flex-wrap: wrap; gap: 0.65rem; margin-top: 1rem; }
.badge { border: 1px solid var(--line); background: rgba(255,255,255,0.06); color: var(--soft); border-radius: 999px; padding: 0.5rem 0.7rem; font-weight: 900; font-size: 0.86rem; }
.badge.earned { background: rgba(95,240,165,0.13); border-color: rgba(95,240,165,0.45); color: var(--good); }
.leaderboard-card { border-radius: var(--radius); padding: 1rem; }
.leader-row { display: grid; grid-template-columns: 34px 1fr auto; gap: 0.75rem; align-items: center; border-bottom: 1px solid var(--line); padding: 0.75rem 0; }
.leader-row:last-child { border-bottom: 0; }
.rank { width: 34px; height: 34px; border-radius: 50%; display: grid; place-items: center; background: rgba(255,255,255,0.08); font-weight: 950; }
.leader-row.me .rank { background: var(--accent); color: #06101d; }
.xp { color: var(--accent-3); font-weight: 950; }
.muted { color: var(--muted); }
.small { font-size: 0.84rem; }

.toast {
  position: fixed;
  left: 50%;
  bottom: 1rem;
  transform: translateX(-50%) translateY(12px);
  opacity: 0;
  pointer-events: none;
  background: #f6f8ff;
  color: #06101d;
  border-radius: 999px;
  padding: 0.7rem 1rem;
  font-weight: 900;
  box-shadow: 0 18px 45px rgba(0,0,0,0.3);
  transition: opacity 160ms ease, transform 160ms ease;
  z-index: 50;
}
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }

.site-footer {
  display: flex;
  justify-content: center;
  gap: 1rem;
  flex-wrap: wrap;
  color: var(--muted);
  border-top: 1px solid var(--line);
  padding: 1.5rem 1rem 2rem;
  font-size: 0.88rem;
}

@media (max-width: 1050px) {
  .site-header { grid-template-columns: 1fr; }
  .workspace-link { justify-self: start; }
  .hero, .split, .playground-layout, .leaderboard-layout { grid-template-columns: 1fr; }
  .card-grid.five { grid-template-columns: repeat(2, minmax(0,1fr)); }
  .activity-strip { grid-template-columns: repeat(2, minmax(0,1fr)); }
}

@media (max-width: 720px) {
  .section-shell { width: min(100% - 1rem, 1180px); }
  .tabs { justify-content: flex-start; overflow-x: auto; flex-wrap: nowrap; padding-bottom: 0.2rem; }
  .tab { white-space: nowrap; }
  .card-grid, .card-grid.five, .course-grid, .glossary-grid, .steps, .activity-strip { grid-template-columns: 1fr; }
  .warning-note { display: block; }
  .inline-form, .prompt-tools { flex-direction: column; }
  .hero { min-height: auto; padding-top: 1rem; }
  h1 { font-size: clamp(2.25rem, 14vw, 4rem); }
}