/* De Stijl: the page is one composition; content owns the largest planes. */
:root {
  color-scheme: light;
  --paper: #F4F1EA;
  --black: #000;
  --red: #D0302A;
  --yellow: #EBC226;
  --blue: #1D3F8C;
  --gray: #deddd8;
  --rule: clamp(6px, 1.5vw, 24px);
  --space: clamp(24px, 5.2vw, 88px);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: var(--paper); color: var(--black); }
button, input { font: inherit; }
button, a, summary { -webkit-tap-highlight-color: transparent; }
button, summary { cursor: pointer; }
a { color: inherit; text-decoration: none; }
button { color: inherit; }
button:disabled { opacity: .35; cursor: default; }
:focus-visible { outline: 3px solid var(--blue); outline-offset: 5px; }
[hidden] { display: none !important; }
#hu-landing { font-family: "Arial", "Microsoft YaHei", "PingFang SC", sans-serif; line-height: 1.65; }
#hu-landing h1, #hu-landing h2, #hu-landing h3, #hu-landing p { margin: 0; }
.hu-wrap { max-width: 1800px; margin: auto; border-inline: var(--rule) solid var(--black); }
.hu-nav { display: flex; justify-content: space-between; align-items: stretch; min-height: 96px; border-bottom: var(--rule) solid var(--black); }
.hu-brand { display: flex; align-items: center; gap: 16px; padding: 20px var(--space); font-size: 26px; font-weight: 900; letter-spacing: -1.4px; }
.hu-links { display: flex; align-items: stretch; }
.hu-nav-cta, .hu-locale-toggle { display: flex; align-items: center; justify-content: center; background: var(--paper); border: 0; border-left: 3px solid var(--black); padding: 20px 32px; font-size: 13px; font-weight: 800; }
.hu-locale-toggle { min-width: 90px; }
.hu-nav-cta:hover, .hu-locale-toggle:hover { background: var(--gray); }
.hu-locale-toggle svg { display: none; }
.hu-hero-top { display: grid; grid-template-columns: minmax(0, 1fr) 25%; border-bottom: var(--rule) solid var(--black); }
.hu-hero-copy { min-width: 0; }
.hu-hero-title { padding: 48px var(--space) 54px; }
.hu-eyebrow, .hu-overline { font-size: 12px; font-weight: 800; letter-spacing: .08em; }
.hu-eyebrow { display: flex; align-items: center; gap: 12px; margin-bottom: 32px !important; }
.hu-eyebrow::before { content: ""; width: 24px; height: 4px; background: var(--black); }
#hu-landing h1 { font-size: clamp(48px, 6.7vw, 112px); font-weight: 900; line-height: 1.24; letter-spacing: -.065em; }
.hu-title-line { display: block; }
.hu-hero-info { display: grid; grid-template-columns: 1.05fr 1fr; border-top: 3px solid var(--black); }
.hu-intro { padding: 32px 26px 36px var(--space); font-size: clamp(13px, 1.05vw, 17px); line-height: 1.9; }
.hu-hero-action { padding: 32px 28px; border-left: 3px solid var(--black); display: flex; flex-direction: column; justify-content: center; }
.hu-actions { display: flex; flex-wrap: wrap; align-items: center; gap: 16px 24px; }
.hu-primary { display: inline-flex; justify-content: center; align-items: center; gap: 24px; padding: 14px 20px; border: 3px solid var(--black); background: var(--paper); font-size: 14px; font-weight: 800; }
.hu-primary::after { content: ""; width: 14px; height: 14px; border-top: 3px solid var(--black); border-right: 3px solid var(--black); }
.hu-primary:hover { background: var(--gray); }
.hu-secondary { font-size: 12px; font-weight: 700; text-decoration: underline; text-underline-offset: 5px; }
.hu-note { margin-top: 18px !important; max-width: 30em; font-size: 11px; line-height: 1.9; }
.hu-composition { border-left: var(--rule) solid var(--black); display: grid; grid-template-rows: minmax(220px, 1fr) 24%; }
.hu-plane-red { background: var(--red); }
.hu-plane-rest { border-top: var(--rule) solid var(--black); background: var(--paper); }
.hu-scene { padding: 36px var(--space) 48px; display: grid; grid-template-columns: minmax(0, 1.25fr) minmax(0, .8fr); gap: 36px 6%; align-items: end; }
.hu-scene-top { grid-column: 1 / -1; display: flex; justify-content: space-between; gap: 20px; font-size: 12px; font-weight: 800; margin-bottom: 12px; }
.hu-scene-top span:last-child { font-size: 11px; font-weight: 400; }
.hu-monitor { border: 8px solid var(--black); min-width: 0; }
.hu-window-head { padding: 12px 20px; display: flex; justify-content: space-between; gap: 16px; font-size: 10px; border-bottom: 3px solid var(--black); }
.hu-window-body { display: grid; grid-template-columns: 48px minmax(0, 1fr); }
.hu-tool-rail { display: flex; flex-direction: column; align-items: center; gap: 12px; padding-top: 24px; border-right: 3px solid var(--black); }
.hu-tool-rail button { width: 32px; height: 38px; padding: 0; background: var(--paper); border: 2px solid transparent; font-size: 11px; font-weight: 800; }
.hu-tool-rail button[aria-pressed=true] { border-color: var(--black); background: var(--gray); }
.hu-exercise { padding: 28px; }
.hu-exercise small, .hu-tablet-screen small { font-size: 10px; }
.hu-exercise h3 { font-size: clamp(17px, 1.5vw, 23px); font-weight: 800; margin: 10px 0 20px !important; }
.hu-problem { font-size: 12px; line-height: 1.8; }
.ink-surface { position: relative; border-top: 2px solid var(--black); margin-top: 28px; }
canvas[data-ink] { display: block; width: 100%; aspect-ratio: 2.7 / 1; touch-action: none; cursor: crosshair; }
.ink-placeholder { position: absolute; inset: 0; display: grid; place-items: center; pointer-events: none; font-size: 11px; }
.hu-tablet { border: 8px solid var(--black); margin-bottom: 0; min-width: 0; }
.hu-tablet-screen { padding: 28px; }
.hu-tablet canvas { aspect-ratio: 1.7 / 1; }
.hu-monitor-foot, .hu-stylus { display: none; }
.hu-scene-caption { grid-column: 1 / -1; display: flex; align-items: center; justify-content: space-between; font-size: 11px; font-weight: 700; letter-spacing: .08em; }
.hu-scene-caption span { display: none; }
.demo-controls { display: flex; flex-wrap: wrap; align-items: center; gap: 10px 20px; border-top: 3px solid var(--black); padding: 24px var(--space) 12px; }
.demo-colors { display: flex; gap: 6px; }
.demo-controls button { display: inline-flex; justify-content: center; align-items: center; min-height: 40px; min-width: 40px; padding: 8px 12px; border: 2px solid var(--black); background: var(--paper); font-size: 11px; font-weight: 700; }
.demo-colors button { padding: 6px; border-color: transparent; }
.demo-colors button[aria-pressed=true] { border-color: var(--black); }
.demo-colors span { width: 22px; height: 22px; background: var(--ink); }
.demo-width { display: flex; align-items: center; gap: 12px; font-size: 11px; }
.demo-width input { appearance: none; width: 100px; height: 4px; background: var(--black); cursor: pointer; }
.demo-width input::-webkit-slider-thumb { appearance: none; width: 14px; height: 22px; background: var(--paper); border: 3px solid var(--black); border-radius: 0; }
.demo-width input::-moz-range-thumb { width: 10px; height: 18px; background: var(--paper); border: 3px solid var(--black); border-radius: 0; }
.demo-width output { width: 28px; }
#demo-status { padding: 8px var(--space) 28px; font-size: 11px; }
.hu-benefits { display: grid; grid-template-columns: 1.2fr 1fr 1fr; border-top: 3px solid var(--black); }
.hu-benefits > span { padding: 26px 20px; text-align: center; font-size: 12px; font-weight: 700; }
.hu-benefits > span + span { border-left: 3px solid var(--black); }
.hu-section { border-top: var(--rule) solid var(--black); }
.hu-section-header { display: grid; grid-template-columns: minmax(0, 1fr) 25%; border-bottom: 3px solid var(--black); }
.hu-section-header > div { padding: 56px var(--space) 60px; }
.hu-overline { margin-bottom: 28px; }
#hu-landing h2 { font-size: clamp(32px, 3.9vw, 60px); line-height: 1.3; font-weight: 900; letter-spacing: -.05em; }
.hu-section-header::after { content: ""; border-left: 3px solid var(--black); }
#hu-clips .hu-section-header { grid-template-columns: minmax(0, 1fr) 17%; }
#hu-clips .hu-section-header::after { background: var(--blue); border-left: var(--rule) solid var(--black); }
.hu-workflow { display: grid; grid-template-columns: minmax(0, .8fr) minmax(0, 1.2fr); }
.hu-steps { display: flex; flex-direction: column; justify-content: center; padding: 36px; gap: 0; }
.hu-step { position: relative; display: grid; grid-template-columns: 38px minmax(0, 1fr); align-items: start; gap: 14px; width: 100%; text-align: left; padding: 28px 20px; border: 0; border-bottom: 2px solid var(--black); background: var(--paper); }
.hu-step:last-child { border-bottom: 0; }
.hu-step[aria-pressed=true] { background: var(--gray); }
.hu-step:hover { background: var(--gray); }
.hu-step-num { font-size: 12px; font-weight: 800; padding-top: 3px; }
.hu-step strong { font-size: 17px; line-height: 1.6; font-weight: 800; }
.hu-work-preview { border-left: 3px solid var(--black); padding: 48px; min-width: 0; }
.hu-mini-top, .hu-mini-bottom { font-size: 11px; font-weight: 700; }
.hu-mini-paper { margin: 26px 0; border: 3px solid var(--black); min-height: 280px; padding: 32px; }
.hu-mini-paper h3 { font-size: 19px; line-height: 1.5; margin-bottom: 24px !important; }
.hu-mini-paper p, .hu-grading { font-size: 12px; }
.hu-detail-line { height: 2px; background: var(--gray); margin: 22px 0; }
.hu-inline-formula { font-size: 26px; font-weight: 800; margin: 20px 0; }
.hu-grading { margin-top: 18px; }
.hu-clips { display: grid; grid-template-columns: minmax(0, .75fr) minmax(0, 1.25fr); align-items: center; }
.hu-clip-stage { padding: clamp(20px, 3vw, 48px); border-left: 3px solid var(--black); position: relative; min-width: 0; }
.hu-clip-stage video { display: block; width: 100%; aspect-ratio: 16 / 10; object-fit: contain; border: 3px solid var(--black); background: var(--paper); }
.hu-clip-toggle { position: absolute; right: calc(clamp(20px, 3vw, 48px) + 16px); bottom: calc(clamp(20px, 3vw, 48px) + 16px); min-height: 44px; padding: 10px 18px; border: 3px solid var(--black); background: var(--paper); font-size: 12px; font-weight: 800; }
.hu-clip-toggle[data-state=playing] .hu-icon-play, .hu-clip-toggle[data-state=paused] .hu-icon-pause { display: none; }
.hu-clip-list { padding: 36px; }
.hu-clip-list .hu-step { padding: 28px 20px 34px; grid-template-columns: 24px minmax(0, 1fr); gap: 14px; }
.hu-clip-list .hu-step strong { font-size: 16px; }
.hu-clip-progress { position: absolute; bottom: 0; left: 0; width: 100%; height: 5px; background: var(--black); transform: scaleX(var(--p, 0)); transform-origin: left; }
.hu-feature-grid { display: grid; grid-template-columns: 1.2fr 1fr; row-gap: 24px; }
.hu-feature { padding: var(--space); display: grid; grid-template-rows: subgrid; grid-row: span 3; gap: 24px; }
.hu-feature + .hu-feature { border-left: 3px solid var(--black); }
.hu-feature h3 { font-size: clamp(24px, 2.3vw, 36px); line-height: 1.4; font-weight: 900; }
.hu-feature p { max-width: 32em; font-size: 14px; line-height: 2; }
.hu-ink-sample { margin-top: 24px; display: flex; align-items: center; gap: 32px; padding-top: 24px; border-top: 3px solid var(--black); }
.hu-ink-sample em { font-size: 72px; line-height: 1; font-style: normal; font-weight: 900; }
.hu-ink-sample span, .hu-local-detail { font-size: 11px; }
.hu-local-detail { border-top: 3px solid var(--black); padding-top: 24px; margin-top: 24px; display: flex; align-items: center; }
.hu-feature-icon { display: none; }
.hu-bottom { display: grid; grid-template-columns: 1fr 1.2fr; }
.hu-bottom > div { padding: var(--space); }
.hu-bottom > div + div { border-left: var(--rule) solid var(--black); }
details { border-bottom: 3px solid var(--black); padding: 24px 0; }
details:first-child { padding-top: 0; }
summary { display: flex; justify-content: space-between; align-items: baseline; gap: 20px; list-style: none; font-size: 15px; font-weight: 800; }
summary::-webkit-details-marker { display: none; }
summary::after { content: "+"; font-size: 24px; font-weight: 400; }
details[open] summary::after { content: "−"; }
details p { margin-top: 24px !important; font-size: 13px; line-height: 2; }
.hu-final { position: relative; display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 40px; padding: 72px var(--space) 72px calc(var(--space) + clamp(32px, 9vw, 150px)); align-items: center; border-top: var(--rule) solid var(--black); }
.hu-final::before { content: ""; position: absolute; top: 0; bottom: 0; left: 0; width: clamp(32px, 9vw, 150px); background: var(--yellow); border-right: 3px solid var(--black); }
#hu-landing .hu-final h2 { font-size: clamp(26px, 3vw, 46px); }
.hu-final p { font-size: 12px; margin-top: 20px !important; max-width: 38em; }
.hu-final .hu-primary { white-space: nowrap; }
.hu-footer { display: flex; justify-content: space-between; gap: 24px; padding: 30px var(--space); border-top: var(--rule) solid var(--black); font-size: 11px; font-weight: 700; }
.hu-footer-links { display: flex; flex-wrap: wrap; gap: 24px; }
.hu-footer a:hover { text-decoration: underline; text-underline-offset: 4px; }
/* Rectilinear controls replace decorative pictograms; recorded product UI is unchanged. */
#hu-landing svg { display: none; }
html[lang=en] #hu-landing h1 { font-size: clamp(40px, 5.4vw, 88px); letter-spacing: -.055em; }
html[lang=en] .hu-intro br { display: none; }
html[lang=en] #hu-landing h2 { font-size: clamp(30px, 3.5vw, 54px); }
@media (min-width: 1800px) { .hu-wrap { border-top: var(--rule) solid var(--black); } }
@media (max-width: 1000px) {
  .hu-hero-top { grid-template-columns: minmax(0, 1fr) 20%; }
  .hu-hero-title { padding-block: 40px; }
  .hu-hero-info { grid-template-columns: 1fr; }
  .hu-intro { padding: 24px var(--space); }
  .hu-hero-action { border-left: 0; padding: 0 var(--space) 32px; }
  .hu-scene { gap: 24px; padding-inline: 28px; grid-template-columns: minmax(0, 1.2fr) minmax(0, .8fr); }
  .hu-exercise, .hu-tablet-screen { padding: 20px; }
  .hu-steps { padding: 20px; }
  .hu-work-preview { padding: 28px; }
  .hu-bottom { grid-template-columns: .85fr 1.15fr; }
  .hu-bottom > div { padding: 40px 28px; }
  .hu-final { grid-template-columns: 1fr; gap: 28px; }
  .hu-final .hu-primary { justify-self: start; }
}
@media (max-width: 680px) {
  .hu-nav { min-height: 72px; }
  .hu-brand { padding: 16px; font-size: 21px; gap: 10px; }
  .hu-nav-cta { padding: 12px; font-size: 11px; }
  .hu-locale-toggle { min-width: 46px; padding: 12px; font-size: 11px; }
  .hu-hero-top { grid-template-columns: minmax(0, 1fr) 12%; }
  .hu-hero-title { padding: 32px 20px 36px; }
  .hu-eyebrow { font-size: 10px; margin-bottom: 28px !important; }
  #hu-landing h1 { font-size: clamp(36px, 8.8vw, 60px); }
  .hu-intro { font-size: 13px; padding: 24px 20px; }
  .hu-intro br { display: none; }
  .hu-hero-action { padding: 0 20px 30px; }
  .hu-primary { font-size: 12px; gap: 14px; padding: 12px 14px; }
  .hu-note { font-size: 10px; }
  .hu-composition { grid-template-rows: 36% 1fr; }
  .hu-scene { grid-template-columns: minmax(0, 1fr); padding: 28px 18px; gap: 24px; }
  .hu-scene-top { flex-direction: column; gap: 6px; margin-bottom: 0; }
  .hu-monitor, .hu-tablet { border-width: 5px; }
  .hu-tablet { width: 84%; justify-self: end; }
  .hu-window-head { padding: 10px; font-size: 9px; }
  .hu-window-head span:last-child { display: none; }
  .hu-window-body { grid-template-columns: 36px minmax(0, 1fr); }
  .hu-exercise, .hu-tablet-screen { padding: 16px; }
  .hu-tool-rail button { width: 26px; }
  .hu-exercise h3 { font-size: 16px; }
  .hu-problem { font-size: 11px; }
  canvas[data-ink] { aspect-ratio: 2 / 1; }
  .hu-scene-caption { font-size: 10px; letter-spacing: 0; }
  .demo-controls { padding: 20px 18px 12px; gap: 12px; }
  .demo-width { gap: 8px; }
  .demo-width input { width: 65px; }
  #demo-status { padding: 8px 18px 24px; }
  .hu-benefits { grid-template-columns: 1fr; }
  .hu-benefits > span { padding: 16px 24px; text-align: left; }
  .hu-benefits > span + span { border-left: 0; border-top: 2px solid var(--black); }
  .hu-section-header, #hu-clips .hu-section-header { grid-template-columns: minmax(0, 1fr) 12%; }
  .hu-section-header > div { padding: 40px 24px; }
  .hu-overline { font-size: 10px; margin-bottom: 24px; }
  #hu-landing h2 { font-size: clamp(28px, 7.4vw, 42px); }
  .hu-workflow, .hu-feature-grid, .hu-bottom { grid-template-columns: minmax(0, 1fr); }
  .hu-steps { padding: 16px; }
  .hu-step { padding: 24px 12px; }
  .hu-step strong { font-size: 14px; }
  .hu-work-preview { border-left: 0; border-top: 3px solid var(--black); padding: 28px 20px; }
  .hu-mini-paper { padding: 24px 18px; }
  .hu-clips { grid-template-columns: minmax(0, 1fr); }
  .hu-clip-list { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); padding: 0; }
  .hu-clip-list .hu-step { padding: 22px 12px; }
  .hu-clip-list .hu-step strong { font-size: 11px; }
  .hu-clip-list .hu-step { border-bottom: 0; }
  .hu-clip-list .hu-step:nth-child(even) { border-left: 3px solid var(--black); }
  .hu-clip-list .hu-step:nth-child(n+3) { border-top: 3px solid var(--black); }
  .hu-clip-stage { padding: 16px; border-left: 0; border-top: 3px solid var(--black); }
  .hu-clip-toggle { right: 24px; bottom: 24px; font-size: 10px; min-height: 36px; padding: 6px 10px; }
  .hu-feature-grid { row-gap: 0; }
  .hu-feature { padding: 40px 24px; display: flex; flex-direction: column; grid-row: auto; }
  .hu-feature + .hu-feature { border-left: 0; border-top: 3px solid var(--black); }
  .hu-bottom > div + div { border-left: 0; border-top: var(--rule) solid var(--black); }
  .hu-feature p { font-size: 13px; }
  .hu-bottom > div { padding: 40px 24px; }
  .hu-final { padding: 40px 24px 40px 48px; }
  .hu-final::before { width: 24px; }
  .hu-footer { flex-direction: column; padding: 24px; }
  .hu-footer > span:first-child { display: flex; flex-wrap: wrap; gap: 8px; }
  .hu-footer > span:first-child span { margin-left: 0 !important; }
  html[lang=en] #hu-landing h1 { font-size: clamp(33px, 8.2vw, 54px); }
  html[lang=en] .hu-nav-cta { max-width: 90px; text-align: center; line-height: 1.4; }
}
@media (prefers-reduced-motion: no-preference) {
  .hu-title-line { animation: hu-reveal .65s cubic-bezier(.2,.6,.3,1) both; }
  .hu-title-line + .hu-title-line { animation-delay: .12s; }
  .hu-plane-red { animation: hu-fill .7s cubic-bezier(.2,.6,.3,1) both; transform-origin: top; }
  .hu-nav { position: relative; }
  .hu-nav::after { content: ""; position: absolute; left: 0; right: 0; bottom: calc(-1 * var(--rule)); height: var(--rule); background: var(--paper); transform-origin: right; animation: hu-line .55s ease-out both; pointer-events: none; }
  @keyframes hu-reveal { from { clip-path: inset(0 100% 0 0); transform: translateX(-12px); } to { clip-path: inset(0); transform: translateX(0); } }
  @keyframes hu-fill { from { transform: scaleY(0); } to { transform: scaleY(1); } }
  @keyframes hu-line { from { transform: scaleX(1); } to { transform: scaleX(0); } }
}
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }