:root {
  color-scheme: dark;
  --ink: #eef8ff;
  --muted: #9cb2c6;
  --surface: #0b1723;
  --surface-2: #101f2e;
  --line: rgba(163, 202, 232, 0.18);
  --accent: #51d9ff;
  --accent-rgb: 81, 217, 255;
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background: #06101a;
  color: var(--ink);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: radial-gradient(circle at 80% 0%, rgba(var(--accent-rgb), .12), transparent 28rem), #06101a; line-height: 1.65; }
a { color: inherit; }
button, input { font: inherit; }
code { font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace; }
.skip-link { position: fixed; left: 1rem; top: -5rem; z-index: 100; background: var(--accent); color: #06101a; padding: .7rem 1rem; border-radius: .4rem; }
.skip-link:focus { top: 1rem; }
.site-header { min-height: 4.75rem; display: flex; align-items: center; gap: 2rem; padding: .8rem max(1.2rem, calc((100vw - 1200px) / 2)); border-bottom: 1px solid var(--line); background: rgba(6, 16, 26, .9); backdrop-filter: blur(14px); position: sticky; top: 0; z-index: 20; }
.brand { display: inline-flex; align-items: center; gap: .7rem; text-decoration: none; font-weight: 900; letter-spacing: -.02em; }
.brand-mark { display: grid; place-items: center; width: 2.25rem; height: 2.25rem; border: 1px solid var(--accent); border-radius: .5rem; color: var(--accent); font-size: .8rem; transform: rotate(-3deg); box-shadow: 3px 3px 0 rgba(var(--accent-rgb), .18); }
.site-header nav { display: flex; gap: 1.25rem; margin-left: auto; }
.site-header nav a, .footer-links a { color: var(--muted); text-decoration: none; font-size: .9rem; }
.site-header nav a:hover, .footer-links a:hover { color: var(--accent); }
.header-cta { text-decoration: none; border: 1px solid var(--accent); color: var(--accent); border-radius: 999px; padding: .45rem .9rem; font-weight: 800; font-size: .84rem; }
.page-shell, .hero, .algorithm-hero, .section, .direct-answer, .final-cta, .sources { width: min(1200px, calc(100% - 2.4rem)); margin-inline: auto; }
.breadcrumbs { display: flex; align-items: center; gap: .55rem; flex-wrap: wrap; padding: 1.1rem 0; font-size: .78rem; color: var(--muted); }
.breadcrumbs a { text-decoration: none; }
.breadcrumbs a:hover { color: var(--accent); }
.hero, .algorithm-hero { display: grid; grid-template-columns: minmax(0, 1.5fr) minmax(17rem, .72fr); gap: 4rem; align-items: center; min-height: 36rem; padding: 4.5rem 0 5.5rem; }
.eyebrow, .kicker { margin: 0 0 .8rem; color: var(--accent); text-transform: uppercase; letter-spacing: .16em; font-size: .73rem; font-weight: 900; }
h1 { margin: 0; max-width: 18ch; font-size: clamp(2.6rem, 6.4vw, 5.6rem); line-height: .96; letter-spacing: -.06em; text-wrap: balance; }
h2 { margin: 0; font-size: clamp(1.85rem, 4vw, 3.15rem); line-height: 1.06; letter-spacing: -.045em; text-wrap: balance; }
h3 { margin: 0; line-height: 1.22; letter-spacing: -.025em; }
p { color: var(--muted); }
.hero-intro { max-width: 64ch; margin: 1.6rem 0 0; font-size: clamp(1rem, 1.6vw, 1.25rem); }
.hero-actions, .button-row, .chip-row { display: flex; gap: .7rem; flex-wrap: wrap; align-items: center; margin-top: 1.7rem; }
.button { display: inline-flex; align-items: center; justify-content: center; min-height: 3rem; padding: .65rem 1.05rem; border: 1px solid var(--line); border-radius: .55rem; color: var(--ink); background: transparent; text-decoration: none; font-weight: 850; cursor: pointer; }
.button.primary { background: var(--accent); border-color: var(--accent); color: #041019; box-shadow: 0 8px 28px rgba(var(--accent-rgb), .18); }
.button.secondary:hover { border-color: var(--accent); color: var(--accent); }
.hero-panel, .algorithm-callout { position: relative; min-height: 22rem; display: flex; flex-direction: column; justify-content: center; border: 1px solid rgba(var(--accent-rgb), .55); border-radius: 1.2rem; padding: 2rem; background: linear-gradient(145deg, rgba(var(--accent-rgb), .15), rgba(12, 28, 41, .7)); box-shadow: 14px 14px 0 rgba(var(--accent-rgb), .08); overflow: hidden; }
.hero-panel::after { content: ""; position: absolute; width: 11rem; height: 11rem; right: -5rem; top: -4rem; border: 2rem solid rgba(var(--accent-rgb), .1); border-radius: 2rem; transform: rotate(24deg); }
.hero-panel > strong { color: var(--accent); font-size: clamp(3.5rem, 7vw, 6.8rem); line-height: 1; letter-spacing: -.08em; }
.hero-badge { align-self: flex-start; margin-bottom: 2rem; padding: .3rem .55rem; border: 1px solid var(--line); border-radius: .35rem; color: var(--muted); font-size: .65rem; letter-spacing: .12em; }
.facts { display: grid; grid-template-columns: repeat(3, 1fr); gap: .7rem; margin-top: 2.1rem; }
.fact { border-top: 1px solid var(--line); padding-top: .7rem; }
.fact strong, .fact span { display: block; }
.fact strong { color: var(--ink); font-size: .85rem; }
.fact span { color: var(--muted); font-size: .67rem; }
.direct-answer { margin-bottom: 7rem; border: 1px solid rgba(var(--accent-rgb), .42); border-left: .32rem solid var(--accent); border-radius: .85rem; padding: clamp(1.6rem, 4vw, 3.2rem); background: linear-gradient(90deg, rgba(var(--accent-rgb), .09), transparent); }
.direct-answer h2 { max-width: 24ch; }
.direct-answer > p:last-child { max-width: 78ch; margin: 1.2rem 0 0; font-size: 1.08rem; }
.section { padding: 4.8rem 0; }
.section-heading { max-width: 47rem; margin-bottom: 2.4rem; }
.section-heading > p:last-child { font-size: 1.05rem; }
.content-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1rem; }
.content-card { position: relative; border: 1px solid var(--line); border-radius: .8rem; padding: 2rem; background: rgba(16, 31, 46, .58); }
.content-card:hover { border-color: rgba(var(--accent-rgb), .5); }
.card-index { display: block; margin-bottom: 1.4rem; color: var(--accent); font-family: monospace; font-weight: 800; }
.content-card p:last-child { margin-bottom: 0; }
.steps { display: grid; grid-template-columns: repeat(5, 1fr); gap: .8rem; padding: 0; list-style: none; }
.steps li { border-top: .24rem solid var(--accent); padding: 1.2rem; background: var(--surface); }
.steps li > span { color: var(--accent); font: 800 .8rem monospace; }
.steps h3 { margin-top: 1rem; font-size: 1rem; }
.steps p { font-size: .86rem; }
.sources { margin-top: 2rem; padding: 1.3rem 1.5rem; border: 1px solid var(--line); border-radius: .7rem; }
.sources h2 { font-size: 1rem; letter-spacing: 0; }
.sources ul { margin-bottom: 0; }
.sources a { color: var(--accent); }
.faq-list { border-top: 1px solid var(--line); }
.faq details { border-bottom: 1px solid var(--line); padding: 1.25rem .2rem; }
.faq summary { cursor: pointer; color: var(--ink); font-weight: 800; list-style-position: outside; }
.faq details p { max-width: 72ch; margin-bottom: 0; }
.card-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: .8rem; }
.link-card { display: flex; min-height: 9rem; flex-direction: column; justify-content: space-between; padding: 1.2rem; border: 1px solid var(--line); border-radius: .65rem; background: rgba(16, 31, 46, .5); text-decoration: none; }
.link-card:hover { border-color: var(--accent); transform: translateY(-2px); }
.link-card span { font-weight: 850; line-height: 1.25; }
.link-card small { color: var(--accent); }
.final-cta { margin-top: 4rem; margin-bottom: 6rem; padding: clamp(2rem, 6vw, 5rem); text-align: center; border: 1px solid rgba(var(--accent-rgb), .45); border-radius: 1.2rem; background: radial-gradient(circle at top, rgba(var(--accent-rgb), .18), transparent 70%); }
.final-cta h2 { max-width: 20ch; margin-inline: auto; }
.final-cta p:not(.kicker) { max-width: 48rem; margin-inline: auto; }
.site-footer { display: grid; grid-template-columns: 1.4fr .8fr; gap: 2rem; align-items: start; padding: 3.2rem max(1.2rem, calc((100vw - 1200px) / 2)); border-top: 1px solid var(--line); background: #040c14; }
.site-footer > div:first-child p { max-width: 34rem; font-size: .85rem; }
.footer-links { display: grid; grid-template-columns: repeat(2, 1fr); gap: .8rem; }
.footer-note { grid-column: 1 / -1; margin: 1rem 0 0; color: #6e8293; font-size: .72rem; }

/* Rich algorithm pages */
.algorithm-hero { min-height: 31rem; }
.chip-row span { border: 1px solid var(--line); border-radius: 999px; padding: .28rem .65rem; color: var(--muted); font-size: .75rem; }
.algorithm-callout { min-height: 15rem; }
.algorithm-callout small { color: var(--accent); text-transform: uppercase; letter-spacing: .13em; }
.algorithm-callout code { margin: 1rem 0; color: var(--ink); font-size: clamp(1.25rem, 3vw, 2rem); line-height: 1.35; }
.algorithm-callout a { color: var(--accent); text-decoration: none; }
.algorithm-lab { border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.lab-grid { display: grid; grid-template-columns: minmax(18rem, .9fr) minmax(20rem, 1.1fr); gap: 2rem; }
.cube-stage { display: grid; place-items: center; min-height: 31rem; border: 1px solid var(--line); border-radius: .8rem; background: radial-gradient(circle, rgba(var(--accent-rgb), .1), transparent 65%), #07111b; }
twisty-player { width: min(100%, 31rem); height: 30rem; }
.lab-controls { display: flex; flex-direction: column; justify-content: center; gap: 1.6rem; }
.control-label { display: block; margin-bottom: .65rem; color: var(--muted); text-transform: uppercase; letter-spacing: .13em; font-size: .7rem; font-weight: 800; }
.control-button, .algorithm-option, .text-button { border: 1px solid var(--line); background: var(--surface); color: var(--ink); cursor: pointer; }
.control-button { border-radius: .45rem; padding: .55rem .8rem; }
.control-button[aria-pressed="true"], .control-button:hover { border-color: var(--accent); color: var(--accent); }
.algorithm-options { display: grid; gap: .55rem; }
.algorithm-option { display: grid; grid-template-columns: 8rem 1fr; gap: .8rem; align-items: center; text-align: left; border-radius: .55rem; padding: .75rem .9rem; }
.algorithm-option.active { border-color: var(--accent); background: rgba(var(--accent-rgb), .1); }
.algorithm-option code { color: var(--muted); overflow-wrap: anywhere; }
.recognition-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: .8rem; }
.recognition-grid article { border: 1px solid var(--line); border-radius: .7rem; padding: 1.2rem; background: var(--surface); }
.recognition-grid article > span { color: var(--accent); font: 750 .7rem monospace; }
.recognition-grid h3 { margin-top: 1rem; }
.recognition-grid p { font-size: .88rem; }
.split-section { display: grid; grid-template-columns: repeat(2, 1fr); gap: 2.5rem; }
.split-section > article { min-width: 0; }
.algorithm-table { display: grid; margin-top: 1.5rem; border-top: 1px solid var(--line); }
.algorithm-table > div { display: grid; grid-template-columns: 8rem minmax(10rem, 1fr); gap: .5rem 1rem; padding: 1rem 0; border-bottom: 1px solid var(--line); }
.algorithm-table code { color: var(--accent); overflow-wrap: anywhere; }
.algorithm-table p { grid-column: 2; margin: 0; font-size: .83rem; }
.setup-code { display: block; margin: 1.5rem 0 1rem; padding: 1rem; border: 1px solid rgba(var(--accent-rgb), .4); border-radius: .55rem; color: var(--accent); background: #050d15; overflow-wrap: anywhere; }
.text-button { border: 0; padding: 0; color: var(--accent); background: none; text-decoration: underline; }
.detail-list { padding-left: 1.4rem; }
.detail-list li { padding: .65rem 0 .65rem .35rem; color: var(--muted); border-bottom: 1px solid var(--line); }
.mistakes li::marker { color: #ff6b6b; }
.trainer-section { display: grid; grid-template-columns: 1.1fr .9fr; gap: 2.5rem; align-items: stretch; border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.timer-button { width: 100%; min-height: 10rem; display: flex; flex-direction: column; align-items: center; justify-content: center; margin-top: 1.5rem; border: 1px solid var(--accent); border-radius: .8rem; background: rgba(var(--accent-rgb), .08); color: var(--ink); cursor: pointer; }
.timer-button.running { background: rgba(255, 107, 107, .1); border-color: #ff6b6b; }
.timer-button span { color: var(--muted); font-size: .77rem; text-transform: uppercase; letter-spacing: .12em; }
.timer-button strong { font-size: clamp(2.8rem, 7vw, 5rem); line-height: 1; letter-spacing: -.06em; }
.stats-panel { display: grid; grid-template-columns: repeat(3, 1fr); align-content: center; gap: .8rem; }
.stats-panel > div { min-height: 7.5rem; display: flex; flex-direction: column; justify-content: center; border: 1px solid var(--line); border-radius: .65rem; padding: 1rem; background: var(--surface); }
.stats-panel span { color: var(--muted); font-size: .76rem; }
.stats-panel strong { font-size: 1.45rem; }
.stats-panel .community-stat { grid-column: 1 / -1; }
.community-stat small { margin-top: .3rem; color: #71879a; }
.video-section video { display: block; width: min(100%, 60rem); aspect-ratio: 16 / 9; margin-inline: auto; border: 1px solid var(--line); border-radius: .85rem; background: #03090e; }
.learning-order { display: grid; grid-template-columns: 1fr auto; gap: 2rem; align-items: center; }
.learning-order > div:first-child { max-width: 47rem; }
.order-badge { display: grid; place-items: center; width: 10rem; aspect-ratio: 1; border: 1px solid var(--accent); border-radius: 50%; background: rgba(var(--accent-rgb), .08); }
.order-badge span { font-size: 3rem; font-weight: 900; line-height: 1; color: var(--accent); }
.order-badge small { color: var(--muted); }

@media (max-width: 960px) {
  .site-header nav { display: none; }
  .header-cta { margin-left: auto; }
  .hero, .algorithm-hero { grid-template-columns: 1fr; gap: 2rem; min-height: 0; padding: 3rem 0 4.5rem; }
  .hero-panel { min-height: 18rem; }
  .steps { grid-template-columns: repeat(2, 1fr); }
  .card-grid, .recognition-grid { grid-template-columns: repeat(2, 1fr); }
  .lab-grid, .trainer-section { grid-template-columns: 1fr; }
}

@media (max-width: 640px) {
  .page-shell, .hero, .algorithm-hero, .section, .direct-answer, .final-cta, .sources { width: min(100% - 1.35rem, 1200px); }
  .site-header { padding-inline: .75rem; }
  .site-header .brand > span:last-child { display: none; }
  .content-grid, .split-section, .steps, .card-grid, .recognition-grid, .site-footer { grid-template-columns: 1fr; }
  .facts { gap: .35rem; }
  .hero-panel { padding: 1.35rem; }
  .section { padding: 3.3rem 0; }
  .algorithm-option { grid-template-columns: 1fr; }
  .algorithm-table > div { grid-template-columns: 1fr; }
  .algorithm-table p { grid-column: 1; }
  .stats-panel { grid-template-columns: 1fr; }
  .stats-panel .community-stat { grid-column: 1; }
  .learning-order { grid-template-columns: 1fr; }
  .order-badge { width: 8rem; }
  .footer-note { grid-column: 1; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition: none !important; animation: none !important; }
}