:root {
  color-scheme: light;
  --bg: #f5f7fb;
  --surface: #ffffff;
  --surface-2: #eef2f8;
  --text: #172033;
  --muted: #5d687c;
  --line: #dce2ec;
  --primary: #6757df;
  --primary-dark: #4a3bbd;
  --accent: #23a889;
  --danger: #c2415b;
  --warning: #9a6515;
  --shadow: 0 18px 48px rgba(31, 42, 68, .10);
  --radius: 18px;
}

[data-theme="dark"] {
  color-scheme: dark;
  --bg: #10131b;
  --surface: #181d28;
  --surface-2: #202736;
  --text: #f0f3fa;
  --muted: #aeb7c8;
  --line: #30394b;
  --primary: #9588ff;
  --primary-dark: #7c6df0;
  --accent: #53d6b7;
  --danger: #ff8198;
  --warning: #f1b85d;
  --shadow: 0 18px 48px rgba(0, 0, 0, .28);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: var(--bg); color: var(--text); font: 16px/1.55 Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; }
button, input { font: inherit; }
a { color: inherit; }
.skip-link { position: fixed; left: 1rem; top: -5rem; z-index: 20; background: var(--text); color: var(--bg); padding: .75rem 1rem; border-radius: 8px; }
.skip-link:focus { top: 1rem; }
.site-header { position: sticky; top: 0; z-index: 10; display: flex; align-items: center; gap: 2rem; min-height: 72px; padding: .8rem clamp(1rem, 4vw, 4rem); border-bottom: 1px solid color-mix(in srgb, var(--line) 75%, transparent); background: color-mix(in srgb, var(--bg) 90%, transparent); backdrop-filter: blur(16px); }
.brand { display: flex; align-items: center; gap: .7rem; margin-right: auto; text-decoration: none; }
.brand-icon { display: block; width: 42px; height: 42px; flex: 0 0 42px; object-fit: contain; border-radius: 50%; background: #050505; box-shadow: 0 8px 20px color-mix(in srgb, var(--primary) 22%, transparent); }
.brand span:last-child { display: grid; line-height: 1.2; }
.brand small { color: var(--muted); font-size: .72rem; }
nav { display: flex; gap: 1.3rem; }
nav a { color: var(--muted); font-size: .9rem; font-weight: 700; text-decoration: none; }
nav a:hover { color: var(--primary); }
.icon-button { width: 40px; height: 40px; border: 1px solid var(--line); border-radius: 12px; color: var(--text); background: var(--surface); cursor: pointer; }
main { overflow: hidden; }
.hero { display: grid; grid-template-columns: minmax(0, 1.4fr) minmax(300px, .6fr); gap: clamp(2rem, 6vw, 6rem); align-items: center; max-width: 1240px; min-height: 520px; margin: auto; padding: clamp(3rem, 8vw, 7rem) clamp(1.2rem, 4vw, 3rem); }
.eyebrow { margin: 0 0 .7rem; color: var(--primary); font-size: .78rem; font-weight: 900; letter-spacing: .14em; text-transform: uppercase; }
h1 { max-width: 800px; margin: 0; font-size: clamp(2.7rem, 6vw, 5.6rem); line-height: .98; letter-spacing: -.055em; }
.lede { max-width: 720px; margin: 1.5rem 0 0; color: var(--muted); font-size: clamp(1.05rem, 1.6vw, 1.3rem); }
.hero-actions, .lesson-actions { display: flex; flex-wrap: wrap; gap: .75rem; margin-top: 1.7rem; }
.button { display: inline-flex; align-items: center; justify-content: center; min-height: 44px; padding: .68rem 1rem; border: 1px solid transparent; border-radius: 11px; font-weight: 800; text-decoration: none; cursor: pointer; transition: transform .15s, background .15s, border-color .15s; }
.button:hover { transform: translateY(-1px); }
.button:focus-visible, button:focus-visible, a:focus-visible, input:focus-visible, summary:focus-visible { outline: 3px solid color-mix(in srgb, var(--primary) 45%, transparent); outline-offset: 2px; }
.button.primary { color: white; background: var(--primary); }
.button.primary:hover { background: var(--primary-dark); }
.button.secondary { border-color: var(--line); color: var(--text); background: var(--surface); }
.button.ghost { color: var(--primary); background: transparent; border-color: color-mix(in srgb, var(--primary) 30%, var(--line)); }
.button.full { width: 100%; }
.connection-card { padding: 1.5rem; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); box-shadow: var(--shadow); }
.status-dot { float: left; width: 13px; height: 13px; margin: .35rem .75rem 0 0; border-radius: 50%; background: var(--warning); box-shadow: 0 0 0 6px color-mix(in srgb, var(--warning) 13%, transparent); }
.status-dot.connected { background: var(--accent); box-shadow: 0 0 0 6px color-mix(in srgb, var(--accent) 13%, transparent); }
.status-dot.missing { background: var(--danger); box-shadow: 0 0 0 6px color-mix(in srgb, var(--danger) 13%, transparent); }
.status-title { margin: 0; font-weight: 900; }
.status-detail { min-height: 2.9rem; margin: .3rem 0 1rem 1.75rem; color: var(--muted); font-size: .9rem; }
dl { display: grid; grid-template-columns: 1fr 1fr; gap: 1px; margin: 0 0 1rem; overflow: hidden; border: 1px solid var(--line); border-radius: 12px; background: var(--line); }
dl div { padding: .75rem; background: var(--surface-2); }
dt { color: var(--muted); font-size: .73rem; font-weight: 800; text-transform: uppercase; }
dd { margin: .15rem 0 0; font-weight: 900; }
.trust-strip { display: flex; justify-content: center; flex-wrap: wrap; gap: 1rem 2.5rem; padding: 1rem; border-block: 1px solid var(--line); color: var(--muted); background: var(--surface); font-size: .88rem; font-weight: 750; }
.section { max-width: 1240px; margin: auto; padding: clamp(4rem, 8vw, 7rem) clamp(1.2rem, 4vw, 3rem); scroll-margin-top: 72px; }
.section-heading { display: flex; align-items: end; justify-content: space-between; gap: 2rem; margin-bottom: 2rem; }
.section-heading h2 { margin: 0; font-size: clamp(2rem, 4vw, 3.25rem); line-height: 1.05; letter-spacing: -.04em; }
.section-heading > p { max-width: 560px; margin: 0; color: var(--muted); }
.quick-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1rem; }
.quick-card, .reference-grid article { position: relative; padding: 1.35rem; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); }
.quick-card h3, .reference-grid h3 { margin: .3rem 0; }
.quick-card p, .reference-grid p { color: var(--muted); }
.step-number { display: grid; place-items: center; width: 34px; height: 34px; color: var(--primary); font-weight: 900; border-radius: 9px; background: color-mix(in srgb, var(--primary) 12%, var(--surface)); }
.check-label { display: flex; gap: .65rem; align-items: start; color: var(--text); font-weight: 700; cursor: pointer; }
.check-label input { width: 19px; height: 19px; margin-top: .15rem; accent-color: var(--primary); }
.result-panel { display: flex; gap: .6rem 1.2rem; flex-wrap: wrap; margin-top: 1rem; padding: 1rem 1.2rem; border: 1px solid var(--line); border-radius: 13px; color: var(--muted); background: var(--surface-2); }
.result-panel strong { color: var(--text); }
.result-panel.pass { border-color: color-mix(in srgb, var(--accent) 55%, var(--line)); background: color-mix(in srgb, var(--accent) 8%, var(--surface)); }
.result-panel.fail { border-color: color-mix(in srgb, var(--danger) 55%, var(--line)); background: color-mix(in srgb, var(--danger) 8%, var(--surface)); }
.course-progress { display: grid; grid-template-columns: auto 150px auto; gap: .7rem; align-items: center; color: var(--muted); font-size: .82rem; }
.course-progress span { width: 150px; height: 7px; overflow: hidden; border-radius: 10px; background: var(--line); }
.course-progress i { display: block; width: 0; height: 100%; background: linear-gradient(90deg, var(--primary), var(--accent)); transition: width .2s; }
.course-progress button, .team-template button { padding: .3rem .55rem; border: 0; color: var(--primary); background: transparent; font-weight: 800; cursor: pointer; }
.lesson-list { display: grid; gap: 1rem; }
.lesson { display: grid; grid-template-columns: 75px 1fr; border: 1px solid var(--line); border-radius: var(--radius); background: var(--surface); box-shadow: 0 8px 22px rgba(31, 42, 68, .035); }
.lesson.done { border-color: color-mix(in srgb, var(--accent) 45%, var(--line)); }
.lesson-index { padding: 1.5rem 1rem; color: var(--muted); font-size: 1.05rem; font-weight: 900; border-right: 1px solid var(--line); }
.lesson-content { min-width: 0; padding: 1.45rem; }
.lesson-title { display: flex; justify-content: space-between; gap: 1rem; }
.lesson-title h3 { margin: 0; font-size: 1.25rem; }
.lesson-title p { margin: .25rem 0 1rem; color: var(--muted); }
.lesson-state { flex: 0 0 auto; height: max-content; padding: .28rem .55rem; border-radius: 99px; color: var(--muted); background: var(--surface-2); font-size: .72rem; font-weight: 800; }
.lesson.done .lesson-state { color: var(--accent); background: color-mix(in srgb, var(--accent) 10%, var(--surface)); }
pre { max-width: 100%; overflow: auto; margin: .6rem 0; padding: 1rem; border: 1px solid var(--line); border-radius: 12px; color: var(--text); background: var(--surface-2); font: .87rem/1.55 "SFMono-Regular", Consolas, "Liberation Mono", monospace; white-space: pre-wrap; word-break: break-word; }
code { font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace; font-size: .9em; }
.expected { padding: .7rem .9rem; border-left: 3px solid var(--primary); color: var(--muted); background: color-mix(in srgb, var(--primary) 5%, transparent); }
.lesson-output { display: block; min-height: 1.4rem; margin-top: .7rem; color: var(--muted); font-size: .88rem; }
.lesson-output.success { color: var(--accent); }
.lesson-output.error { color: var(--danger); }
.team-template { margin-top: 1rem; padding: 1rem; border: 1px solid var(--line); border-radius: 12px; background: var(--surface-2); }
.team-template button { float: right; }
.warning { color: var(--warning); }
.reference-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 1rem; }
.reference-grid article { min-height: 180px; }
.reference-grid h3 { font-size: 1rem; }
.faq { padding-top: 2rem; }
details { border-top: 1px solid var(--line); }
details:last-child { border-bottom: 1px solid var(--line); }
summary { padding: 1.2rem 0; font-weight: 850; cursor: pointer; }
details p { max-width: 850px; margin: -.5rem 0 1.2rem; color: var(--muted); }
footer { display: flex; justify-content: space-between; gap: 1rem; padding: 2rem clamp(1.2rem, 4vw, 4rem); border-top: 1px solid var(--line); color: var(--muted); font-size: .85rem; }
.noscript { position: fixed; inset: auto 1rem 1rem; padding: 1rem; border-radius: 10px; color: white; background: var(--danger); }

@media (max-width: 900px) {
  nav { display: none; }
  .hero { grid-template-columns: 1fr; min-height: auto; }
  .quick-grid, .reference-grid { grid-template-columns: 1fr 1fr; }
  .section-heading { align-items: start; flex-direction: column; }
}

@media (max-width: 620px) {
  .site-header { gap: .7rem; }
  .brand small { display: none; }
  .hero { padding-top: 3rem; }
  .quick-grid, .reference-grid { grid-template-columns: 1fr; }
  .lesson { grid-template-columns: 1fr; }
  .lesson-index { padding: .7rem 1.2rem; border-right: 0; border-bottom: 1px solid var(--line); }
  .lesson-title { flex-direction: column; }
  .lesson-state { align-self: start; }
  .course-progress { grid-template-columns: auto 1fr auto; width: 100%; }
  .course-progress span { width: auto; }
  footer { flex-direction: column; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition-duration: .01ms !important; }
}