:root {
  color-scheme: dark;
  --bg: #090d16;
  --bg-2: #0f1729;
  --panel: #121a2b;
  --panel-2: #182338;
  --border: #2b3956;
  --text: #eef3ff;
  --muted: #9db0d4;
  --accent: #78b8ff;
  --success: #7af0a5;
  --warn: #ffd36b;
  --danger: #ff8f8f;
  --radius: 18px;
  --shadow: 0 18px 55px rgba(0, 0, 0, 0.34);
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  font-family: Inter, ui-sans-serif, system-ui, sans-serif;
  background: radial-gradient(circle at top, #111b31 0%, var(--bg) 42%);
  color: var(--text);
  min-height: 100vh;
}
body.overlay-open { overflow: hidden; }
a { color: var(--accent); }
code { background: #0c1322; border: 1px solid #22314d; border-radius: 8px; padding: 2px 6px; color: #dbeafe; }
pre { margin: 0; background: #0c1322; border: 1px solid #22314d; border-radius: 14px; padding: 14px; overflow-x: auto; white-space: pre-wrap; font-family: ui-monospace, SFMono-Regular, Menlo, monospace; }
.app-shell { max-width: 1400px; margin: 0 auto; padding: 24px 18px 56px; display: grid; grid-template-columns: 320px minmax(0, 1fr); gap: 20px; }
.sidebar { position: sticky; top: 0; align-self: start; display: grid; gap: 16px; padding-top: 6px; }
.sidebar-head h1,.hero h2,.section-card h3,.login-panel h2 { letter-spacing: -0.03em; }
.sidebar-head h1 { margin: 4px 0 10px; font-size: 2rem; }
.eyebrow { color: var(--muted); text-transform: uppercase; letter-spacing: 0.12em; font-size: 12px; }
.sidebar-copy,.muted,.section-card p,.section-card li,.banner,.raccoon-callout p,.small { color: var(--muted); line-height: 1.6; }
.card,.section-card { background: linear-gradient(180deg, rgba(255,255,255,.02), rgba(255,255,255,0)), var(--panel); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow); }
.card { padding: 18px; }
.lesson-body { display: grid; gap: 16px; }
.hero { padding: 24px; margin-bottom: 16px; }
.hero-top,.progress-row,.lesson-nav-item,.nav-controls,.copy-row { display: flex; align-items: center; justify-content: space-between; gap: 12px; }
.chip { display: inline-flex; align-items: center; gap: 8px; background: rgba(120,184,255,.12); color: var(--accent); border: 1px solid rgba(120,184,255,.25); padding: 7px 11px; border-radius: 999px; font-size: 12px; font-weight: 700; }
.chip-muted { background: rgba(255,255,255,.04); color: var(--muted); border-color: rgba(255,255,255,.08); }
.progress-bar { height: 8px; margin: 10px 0 4px; border-radius: 999px; overflow: hidden; background: #1b2336; border: 1px solid var(--border); }
.progress-fill { height: 100%; background: linear-gradient(90deg, var(--accent), #b69cff); width: 10%; }
.lesson-nav { display: grid; gap: 8px; max-height: calc(100vh - 330px); overflow: auto; }
.lesson-nav-item { width: 100%; background: var(--panel-2); border: 1px solid var(--border); border-radius: 12px; padding: 11px 12px; text-align: left; color: var(--text); cursor: pointer; }
.lesson-nav-item:hover { border-color: #47608e; }
.lesson-nav-item.active { border-color: var(--accent); background: rgba(120,184,255,.08); }
.lesson-nav-meta { font-size: 12px; color: var(--muted); }
.badge { font-size: 11px; padding: 4px 7px; border-radius: 999px; }
.badge.done { background: rgba(122,240,165,.12); color: var(--success); }
.badge.locked { background: rgba(255,143,143,.10); color: var(--danger); }
.badge.ready { background: rgba(255,211,107,.10); color: var(--warn); }
.raccoon-callout { margin-top: 18px; padding: 16px; border-radius: 16px; background: rgba(120,184,255,.08); border: 1px solid rgba(120,184,255,.22); display: grid; grid-template-columns: 52px 1fr; gap: 12px; align-items: start; }
.raccoon-face { width: 52px; height: 52px; display: grid; place-items: center; background: linear-gradient(180deg, #23304c, #1a2439); border-radius: 16px; font-size: 27px; }
.section-card { padding: 20px; }
.section-card h3 { margin: 0 0 12px; font-size: 1.5rem; }
.quiz-question { margin-top: 14px; padding: 14px; border-radius: 14px; background: var(--panel-2); border: 1px solid var(--border); }
.question-title { margin-bottom: 10px; font-weight: 700; line-height: 1.5; }
.option { display: flex; gap: 10px; align-items: flex-start; padding: 10px 12px; border-radius: 12px; cursor: pointer; }
.option:hover { background: rgba(255,255,255,.04); }
.option.correct { background: rgba(122,240,165,.08); border: 1px solid rgba(122,240,165,.25); }
.option.incorrect { background: rgba(255,143,143,.08); border: 1px solid rgba(255,143,143,.22); }
.button-row { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 16px; }
button,.auth-form input { appearance: none; border: 1px solid var(--border); background: #1a2337; color: var(--text); border-radius: 12px; padding: 11px 14px; font: inherit; }
button { cursor: pointer; }
button:hover { background: #212d46; border-color: #466186; }
button.primary { background: linear-gradient(180deg, #2e6cff, #2353d3); }
button.success { background: linear-gradient(180deg, #1f7f54, #185f40); }
button:disabled { opacity: .45; cursor: not-allowed; }
.small-button { padding: 8px 10px; font-size: 12px; }
.banner,.feedback,.notice { padding: 14px 16px; border-radius: 14px; border: 1px solid transparent; }
.feedback.success,.notice.success { background: rgba(122,240,165,.08); border-color: rgba(122,240,165,.24); color: var(--success); }
.feedback.error,.notice.error,.banner.error { background: rgba(255,143,143,.08); border-color: rgba(255,143,143,.22); color: var(--danger); }
.notice.warn,.banner.warn { background: rgba(255,211,107,.08); border-color: rgba(255,211,107,.22); color: var(--warn); }
.lesson-locked { opacity: .46; pointer-events: none; filter: blur(1px); }
.tinylab-frame { width: 100%; min-height: 760px; border: 1px solid var(--border); border-radius: 16px; background: #0b1120; }
.copy-area { margin-top: 12px; }
.copy-row { margin-top: 12px; }
.nav-controls { margin-top: 18px; }
.profile-card { display: grid; gap: 10px; }
.profile-card h3 { margin: 0; }
.login-overlay {
  position: fixed;
  inset: 0;
  z-index: 30;
  display: grid;
  place-items: center;
  padding: 24px;
  background:
    radial-gradient(circle at top, rgba(120,184,255,.16), transparent 30%),
    rgba(7, 11, 19, .82);
  backdrop-filter: blur(12px);
}
.login-panel {
  width: min(100%, 720px);
  padding: 26px;
  position: relative;
  overflow: hidden;
  background:
    radial-gradient(circle at top right, rgba(120,184,255,.16), transparent 32%),
    linear-gradient(180deg, rgba(255,255,255,.03), rgba(255,255,255,0)),
    var(--panel);
}
.login-panel h2 { margin: 14px 0 10px; font-size: clamp(2rem, 3vw, 2.8rem); }
.overlay-raccoon { margin-top: 20px; }
.auth-form { display: grid; gap: 14px; margin-top: 20px; }
.auth-form label { display: grid; gap: 6px; }
.auth-form label span { font-size: 12px; color: var(--muted); text-transform: uppercase; letter-spacing: .08em; }
.auth-form input { background: #0f1729; }
.auth-form input:focus { outline: 2px solid rgba(120,184,255,.22); border-color: var(--accent); }
.auth-actions { align-items: center; }
.overlay-note { margin: 16px 0 0; }
.hidden { display: none !important; }
@media (max-width: 980px) {
  .app-shell { grid-template-columns: 1fr; }
  .sidebar { position: static; }
  .lesson-nav { max-height: none; }
}
@media (max-width: 720px) {
  .app-shell { padding: 18px 14px 44px; }
  .card,.section-card,.login-panel { padding: 16px; }
  .hero { padding: 18px; }
  .login-overlay { padding: 16px; }
  .login-panel h2 { font-size: 1.9rem; }
  .raccoon-callout { grid-template-columns: 1fr; }
  .raccoon-face { width: 48px; height: 48px; }
  .auth-actions > * { width: 100%; }
}