/* ============================================================
   EDYOU OS — design system
   Lexend display / IBM Plex Sans body / IBM Plex Mono technical.
   Flat, authored, product-first. Brand blue derived from the
   real EDYOU OS logo and wallpaper assets.
   ============================================================ */

/* ---------- Tokens ---------- */
:root {
  --bg-0: #0a0e16;
  --bg-1: #0d1119;
  --bg-2: #121724;
  --bg-3: #171e2d;
  --bg-4: #1e2638;

  --line-1: rgba(196, 208, 234, 0.10);
  --line-2: rgba(196, 208, 234, 0.18);
  --line-3: rgba(196, 208, 234, 0.32);

  --ink-1: #f4f7fc;
  --ink-2: #c3cce0;
  --ink-3: #b7c2d9;

  --accent: #4d8ff2;
  --accent-2: #7db4ff;
  --accent-3: #93c5ff;
  --accent-ink: #061224;
  --accent-soft: rgba(77, 143, 242, 0.13);

  --font-display: "Lexend", "Segoe UI", system-ui, sans-serif;
  --font-sans: "IBM Plex Sans", "Segoe UI", system-ui, sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, "Cascadia Code", "SF Mono", Consolas, monospace;

  --r-lg: 14px;
  --r-md: 10px;
  --r-sm: 6px;

  --wrap: 1180px;
  --gutter: clamp(20px, 4vw, 48px);
  --header-h: 68px;
  --section-y: clamp(88px, 14vh, 150px);
}

/* ---------- Reset ---------- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; scroll-padding-top: calc(var(--header-h) + 16px); }

body {
  font-family: var(--font-sans);
  background: var(--bg-1);
  color: var(--ink-1);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

img { display: block; max-width: 100%; }
a { color: inherit; }
::selection { background: rgba(77, 143, 242, 0.32); }

:focus-visible {
  outline: 2px solid var(--accent-2);
  outline-offset: 3px;
  border-radius: 3px;
}

[hidden] { display: none !important; }

/* ---------- Typography ---------- */
h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 600;
}

.display {
  font-size: clamp(2.4rem, 5.6vw, 4.4rem);
  line-height: 1.06;
  font-weight: 600;
  letter-spacing: -0.02em;
  text-wrap: balance;
  max-width: 20ch;
}

.h-xl {
  font-size: clamp(1.8rem, 3.4vw, 2.7rem);
  line-height: 1.12;
  font-weight: 600;
  letter-spacing: -0.015em;
  text-wrap: balance;
}

.h-lg {
  font-size: clamp(1.3rem, 2.2vw, 1.8rem);
  line-height: 1.2;
  font-weight: 600;
  letter-spacing: -0.005em;
}

.lead {
  font-size: clamp(1.02rem, 1.5vw, 1.18rem);
  line-height: 1.65;
  color: var(--ink-2);
  max-width: 60ch;
}

.muted { color: var(--ink-2); }
.faint { color: var(--ink-3); }

.meta {
  font-family: var(--font-mono);
  font-size: 0.8rem;
  letter-spacing: 0.02em;
  color: var(--ink-3);
}

code {
  font-family: var(--font-mono);
  font-size: 0.86em;
  color: var(--accent-3);
  background: rgba(147, 197, 255, 0.08);
  border: 1px solid var(--line-1);
  border-radius: 4px;
  padding: 1px 6px;
}

/* ---------- Layout ---------- */
.wrap {
  max-width: var(--wrap);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.section { padding-block: var(--section-y); }

.section-lead {
  margin-bottom: clamp(40px, 7vh, 64px);
  max-width: 66ch;
}
.section-lead .lead { margin-top: 18px; }

.split {
  display: grid;
  grid-template-columns: minmax(0, 5fr) minmax(0, 7fr);
  gap: clamp(40px, 6vw, 72px);
  align-items: start;
}
.split-wide { grid-template-columns: minmax(0, 6fr) minmax(0, 6fr); }
.split-lead .lead { margin-top: 20px; }

/* ---------- Buttons ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 12px 22px;
  border-radius: var(--r-sm);
  font-family: var(--font-sans);
  font-size: 0.94rem;
  font-weight: 600;
  letter-spacing: 0.01em;
  text-decoration: none;
  cursor: pointer;
  border: 1px solid transparent;
  transition: background-color 0.18s ease, border-color 0.18s ease, color 0.18s ease;
  line-height: 1;
  white-space: nowrap;
}
.btn svg { width: 16px; height: 16px; flex-shrink: 0; }

.btn-primary {
  background: var(--accent);
  color: var(--accent-ink);
}
.btn-primary:hover { background: var(--accent-2); }

.btn-ghost {
  background: transparent;
  color: var(--ink-1);
  border-color: var(--line-2);
}
.btn-ghost:hover { border-color: var(--accent-2); color: var(--accent-3); }

.btn-lg { padding: 16px 30px; font-size: 1rem; }

.btn[aria-disabled="true"] {
  opacity: 0.45;
  cursor: not-allowed;
  pointer-events: none;
}

/* ---------- Header ---------- */
.site-header {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 60;
  height: var(--header-h);
  display: flex;
  align-items: center;
  border-bottom: 1px solid transparent;
  transition: background-color 0.25s ease, border-color 0.25s ease, backdrop-filter 0.25s ease;
}
.site-header.is-scrolled {
  background: rgba(9, 12, 19, 0.85);
  -webkit-backdrop-filter: blur(14px);
  backdrop-filter: blur(14px);
  border-color: var(--line-1);
}
.site-header .wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  gap: 24px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
  color: var(--ink-1);
}
.brand-mark {
  width: 34px;
  height: 34px;
  border-radius: 8px;
  object-fit: cover;
}
.brand-name {
  font-family: var(--font-display);
  font-size: 1.02rem;
  font-weight: 600;
  letter-spacing: 0.01em;
}
.brand-name .os { color: var(--ink-3); font-weight: 500; }

.site-nav { display: flex; align-items: center; gap: 4px; }
.site-nav a.nav-link {
  color: var(--ink-2);
  text-decoration: none;
  font-size: 0.9rem;
  font-weight: 500;
  padding: 8px 13px;
  border-radius: var(--r-sm);
  transition: color 0.15s ease, background-color 0.15s ease;
}
.site-nav a.nav-link:hover { color: var(--ink-1); background: rgba(196, 208, 234, 0.07); }
.site-nav .nav-cta { margin-left: 10px; }

.nav-toggle {
  display: none;
  background: none;
  border: 1px solid var(--line-2);
  border-radius: var(--r-sm);
  color: var(--ink-1);
  width: 42px;
  height: 42px;
  cursor: pointer;
  align-items: center;
  justify-content: center;
}
.nav-toggle svg { width: 20px; height: 20px; }

.mobile-menu {
  position: fixed;
  inset: 0;
  z-index: 55;
  background: var(--bg-1);
  display: none;
  flex-direction: column;
  padding: calc(var(--header-h) + 24px) var(--gutter) 40px;
}
.mobile-menu.open { display: flex; }
.mobile-menu a {
  color: var(--ink-1);
  text-decoration: none;
  font-size: 1.6rem;
  font-weight: 600;
  font-family: var(--font-display);
  padding: 14px 0;
  border-bottom: 1px solid var(--line-1);
  letter-spacing: -0.01em;
}
.mobile-menu a:hover { color: var(--accent-3); }
.mobile-menu .mm-cta {
  margin-top: 24px;
  border: none;
  align-self: flex-start;
  font-family: var(--font-sans);
  font-size: 0.94rem;
}

/* ---------- Hero ---------- */
.hero {
  position: relative;
  padding-top: calc(var(--header-h) + clamp(48px, 8vh, 88px));
  padding-bottom: clamp(48px, 8vh, 80px);
}
.hero .lead { margin-top: 22px; }

.hero-actions {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  margin-top: 32px;
}

.hero-meta {
  margin-top: 26px;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--ink-3);
}

.hero-rotate {
  color: var(--accent);
  display: inline-grid;
  grid-template-rows: 1fr;
  vertical-align: bottom;
  line-height: 1.15;
  overflow: hidden;
}
.hero-rotate > span {
  grid-row: 1;
  grid-column: 1;
  white-space: nowrap;
  opacity: 0;
  transform: translateY(100%);
  transition: opacity 0.15s ease, transform 0.3s ease;
}
.hero-rotate > span.active {
  opacity: 1;
  transform: translateY(0);
}
.hero-rotate > span.exit {
  opacity: 0;
  transform: translateY(-100%);
}

.hero-fig {
  margin-top: clamp(40px, 7vh, 64px);
  animation: figIn 0.7s ease both;
}
.hero-fig img {
  width: 100%;
  height: auto;
  border: 1px solid var(--line-2);
  border-radius: var(--r-lg);
  background: var(--bg-3);
  box-shadow: 0 30px 70px -48px rgba(0, 0, 0, 0.85);
}
@keyframes figIn {
  from { opacity: 0; transform: translateY(14px); }
  to { opacity: 1; transform: none; }
}

/* ---------- Tech strip ---------- */
.tech-strip {
  border-top: 1px solid var(--line-1);
  border-bottom: 1px solid var(--line-1);
  background: var(--bg-2);
}
.tech-strip .wrap {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 0;
  align-items: center;
  padding-block: 22px;
}
.tech-strip .t-item {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  letter-spacing: 0.05em;
  color: var(--ink-2);
  display: inline-flex;
  align-items: center;
  gap: 14px;
  padding-inline: 22px;
}
.tech-strip .t-item:first-child { padding-left: 0; }
.tech-strip .t-item:not(:first-child) { border-left: 1px solid var(--line-1); }
.tech-strip .t-item b { color: var(--ink-1); font-weight: 550; }
.tech-strip .t-item em {
  font-style: normal;
  color: var(--accent-3);
}

/* ---------- The problem ---------- */
.problem-list {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px 48px;
  list-style: none;
}
.problem-list li { padding-top: 22px; border-top: 1px solid var(--line-1); }
.problem-list h3 { font-size: 1.08rem; font-weight: 600; }
.problem-list p {
  color: var(--ink-2);
  font-size: 0.95rem;
  margin-top: 8px;
  max-width: 42ch;
}

/* ---------- The experience ---------- */
.experience { background: var(--bg-2); }
.exp-tools {
  margin-top: 32px;
  display: grid;
  gap: 16px;
  list-style: none;
}
.exp-tools div {
  display: grid;
  grid-template-columns: minmax(0, 4fr) minmax(0, 6fr);
  gap: 8px 20px;
  align-items: baseline;
  padding-top: 14px;
  border-top: 1px solid var(--line-1);
}
.exp-tools dt { font-size: 0.98rem; font-weight: 600; }
.exp-tools dd { color: var(--ink-2); font-size: 0.9rem; }
.exp-fig img {
  width: 100%;
  height: auto;
  border: 1px solid var(--line-2);
  border-radius: var(--r-lg);
  background: var(--bg-3);
}
.exp-fig figcaption {
  margin-top: 14px;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--ink-3);
}

/* ---------- Why it's different ---------- */
.principles .split-lead { position: sticky; top: calc(var(--header-h) + 32px); }
.principles-lead .p-hint {
  margin-top: 22px;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--ink-3);
}
.principles-list { display: grid; }
.principle-item { border-top: 1px solid var(--line-1); }
.principle-item:last-of-type { border-bottom: 1px solid var(--line-1); }
.principle-head {
  display: grid;
  grid-template-columns: minmax(0, 5fr) minmax(0, 8fr) 20px;
  align-items: center;
  gap: 20px;
  width: 100%;
  padding: 24px 4px;
  background: none;
  border: none;
  color: inherit;
  font: inherit;
  text-align: left;
  cursor: pointer;
}
.principle-head .ph-title {
  font-family: var(--font-display);
  font-size: 1.18rem;
  font-weight: 600;
  color: var(--ink-1);
  transition: color 0.18s ease;
}
.principle-head .ph-summary { color: var(--ink-2); font-size: 0.95rem; }
.principle-head .ph-ind {
  width: 16px;
  height: 16px;
  color: var(--ink-3);
  transition: transform 0.25s ease, color 0.25s ease;
}
.principle-head:hover .ph-title { color: var(--accent-3); }
.principle-head[aria-expanded="true"] .ph-title { color: var(--ink-1); }
.principle-head[aria-expanded="true"] .ph-ind { transform: rotate(180deg); color: var(--accent-3); }

.principle-panel {
  display: grid;
  grid-template-rows: 0fr;
  transition: grid-template-rows 0.3s ease;
}
.principle-panel.open { grid-template-rows: 1fr; }
.pp-body { overflow: hidden; min-height: 0; padding-inline: 4px; }
.pp-body p { color: var(--ink-2); font-size: 0.95rem; max-width: 58ch; }
.pp-body p:first-child { padding-bottom: 16px; }
.pp-body .p-meta {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--ink-3);
  margin-top: 0;
  padding-bottom: 32px;
}

/* ---------- Explore ---------- */
.explorer { background: var(--bg-2); }
.exp-bar {
  position: relative;
  display: flex;
  gap: 4px;
  border-bottom: 1px solid var(--line-1);
  margin-bottom: 40px;
  overflow-x: auto;
  scrollbar-width: none;
}
.exp-bar::-webkit-scrollbar { display: none; }
.exp-bar::after {
  content: '';
  position: absolute;
  bottom: -1px;
  left: var(--tab-left, 0);
  width: var(--tab-width, 0);
  height: 2px;
  background: var(--accent);
  border-radius: 1px 1px 0 0;
  transition: left 0.3s cubic-bezier(.4,0,.2,1), width 0.3s cubic-bezier(.4,0,.2,1);
  pointer-events: none;
}
.exp-bar::-webkit-scrollbar { display: none; }
.exp-tab {
  display: grid;
  gap: 2px;
  text-align: left;
  background: none;
  border: none;
  border-radius: 0;
  padding: 14px 18px;
  cursor: pointer;
  color: var(--ink-3);
  white-space: nowrap;
  flex-shrink: 0;
  transition: color 0.15s ease;
}
.exp-tab .e-t { font-family: var(--font-display); font-size: 0.95rem; font-weight: 600; }
.exp-tab:hover { color: var(--ink-1); }
.exp-tab[aria-selected="true"] { color: var(--ink-1); }

.exp-content { min-height: 320px; }
.exp-pane { display: none; }
.exp-pane.active { display: block; animation: paneIn 0.28s ease; }
@keyframes paneIn {
  from { opacity: 0; transform: translateY(6px); }
  to { opacity: 1; transform: none; }
}

/* Pane head */
.ep-head {
  display: flex;
  gap: 16px;
  align-items: flex-start;
  margin-bottom: 32px;
}
.ep-head img { width: 44px; height: 44px; flex-shrink: 0; }
.ep-head h3 { font-family: var(--font-display); font-size: 1.3rem; font-weight: 600; margin-bottom: 6px; }
.ep-head p { color: var(--ink-2); font-size: 0.92rem; max-width: 36ch; }

/* Feature grid */
.ep-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0;
}
.ep-feat {
  display: grid;
  grid-template-columns: 28px minmax(0, 1fr) auto;
  gap: 14px;
  align-items: center;
  padding: 14px 16px 14px 0;
  border-top: 1px solid var(--line-1);
  color: inherit;
  text-decoration: none;
}
.ep-feat:nth-child(-n+2) { border-top: none; }
.ep-feat img { width: 22px; height: 22px; }
.ep-feat b { display: block; font-size: 0.92rem; font-weight: 600; color: var(--ink-1); }
.ep-feat small { display: block; font-size: 0.82rem; color: var(--ink-3); margin-top: 2px; }
.ep-feat em {
  font-style: normal;
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent-3);
  white-space: nowrap;
}
a.ep-feat:hover { background: rgba(196, 208, 234, 0.04); border-radius: var(--r-sm); }
a.ep-feat:hover b { color: var(--accent-3); }

/* Apps grid */
.ep-label {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--ink-3);
  margin-bottom: 20px;
}
.ep-apps {
  display: grid;
  grid-template-columns: repeat(6, minmax(0, 1fr));
  gap: 28px 16px;
  justify-items: center;
}
.ep-app {
  display: grid;
  justify-items: center;
  gap: 8px;
  opacity: 0;
  animation: appIn 0.42s cubic-bezier(0.2, 0.7, 0.3, 1.15) forwards;
  animation-delay: calc(var(--i) * 45ms);
}
.ep-app img { width: 52px; height: 52px; transition: transform 0.18s ease, filter 0.18s ease; }
.ep-app span { font-size: 0.78rem; color: var(--ink-2); }
.ep-app:hover img { transform: translateY(-3px) scale(1.08); filter: drop-shadow(0 8px 16px rgba(77, 143, 242, 0.35)); }
.ep-app:hover span { color: var(--accent-3); }
@keyframes appIn {
  from { opacity: 0; transform: translateY(12px) scale(0.94); }
  to { opacity: 1; transform: none; }
}

/* Office list */
.ep-list { max-width: 520px; }
.ep-list-row {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  align-items: baseline;
  padding: 14px 0;
  border-top: 1px solid var(--line-1);
}
.ep-list-row:first-child { border-top: none; padding-top: 2px; }
.ep-list-row span { font-size: 0.96rem; font-weight: 600; }
.ep-list-row em {
  font-style: normal;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  letter-spacing: 0.04em;
  color: var(--ink-3);
  white-space: nowrap;
}

/* ---------- For schools ---------- */
.schools-grid {
  display: grid;
  grid-template-columns: minmax(0, 5fr) minmax(0, 7fr);
  gap: 64px;
  align-items: start;
}
.schools-aside { position: sticky; top: calc(var(--header-h) + 32px); }
.schools-aside .lead { margin-top: 20px; }
.schools-aside .btn { margin-top: 28px; }
.schools-points {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0 48px;
  list-style: none;
}
.schools-points li {
  padding: 0 0 34px 22px;
  border-left: 1px solid var(--line-1);
}
.schools-points h4 { font-size: 1.05rem; margin-bottom: 7px; }
.schools-points p { color: var(--ink-2); font-size: 0.93rem; }

/* ---------- Hardware ---------- */
.hardware { background: var(--bg-2); }
.spec-grid {
  display: grid;
  grid-template-columns: minmax(0, 5fr) minmax(0, 7fr);
  gap: clamp(40px, 6vw, 72px);
  align-items: start;
}
.spec-intro { position: sticky; top: calc(var(--header-h) + 32px); }
.spec-intro .lead { margin-top: 20px; }

.spec-main { min-width: 0; }
.req-table { width: 100%; border-collapse: collapse; }
.req-table th {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  font-weight: 500;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-3);
  text-align: left;
  padding: 0 20px 12px 0;
  border-bottom: 1px solid var(--line-2);
}
.req-table td {
  padding: 16px 20px 16px 0;
  border-bottom: 1px solid var(--line-1);
  color: var(--ink-2);
  font-size: 0.94rem;
}
.req-table td:first-child { color: var(--ink-1); font-weight: 550; white-space: nowrap; }
.req-table tr:last-child td { border-bottom: none; }
.req-table td b { color: var(--ink-1); font-weight: 550; }

.spec-limits {
  margin-top: 38px;
  padding-top: 28px;
  border-top: 1px solid var(--line-2);
}
.spec-limits h3 {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  font-weight: 500;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-3);
  margin-bottom: 18px;
}
.req-note { list-style: none; display: grid; gap: 12px; }
.req-note li {
  display: flex;
  gap: 12px;
  color: var(--ink-2);
  font-size: 0.92rem;
  max-width: 56ch;
}
.req-note li::before { content: "·"; color: var(--accent-3); flex-shrink: 0; }

/* ---------- Open source ---------- */
.os-grid {
  display: grid;
  grid-template-columns: minmax(0, 6fr) minmax(0, 6fr);
  gap: clamp(40px, 6vw, 72px);
  align-items: start;
}
.os-copy .lead { margin-top: 20px; }

.os-verbs {
  margin-top: 30px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  list-style: none;
}
.os-verbs a {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  padding: 15px 18px;
  border: 1px solid var(--line-1);
  border-radius: var(--r-md);
  text-decoration: none;
  color: var(--ink-1);
  font-weight: 550;
  font-size: 0.95rem;
  transition: border-color 0.18s ease;
}
.os-verbs a:hover { border-color: var(--accent-2); }
.os-verbs svg { width: 16px; height: 16px; color: var(--ink-3); }

.license-card {
  margin-top: 22px;
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 18px 22px;
  border: 1px solid var(--line-2);
  border-radius: var(--r-md);
  background: var(--bg-2);
  text-decoration: none;
  color: var(--ink-1);
  transition: border-color 0.18s ease;
}
.license-card:hover { border-color: var(--accent-2); }
.license-card .lc-logo {
  width: 42px;
  height: 42px;
  border-radius: 8px;
  object-fit: cover;
}
.license-card h4 { font-size: 0.98rem; }
.license-card p { color: var(--ink-3); font-size: 0.8rem; font-family: var(--font-mono); }
.license-card svg { margin-left: auto; color: var(--ink-3); width: 20px; height: 20px; flex-shrink: 0; }

.os-build .meta { margin-bottom: 12px; }
.codeblock {
  border: 1px solid var(--line-2);
  border-radius: var(--r-md);
  background: var(--bg-2);
  padding: 20px 22px;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.82rem;
  line-height: 1.85;
  color: var(--ink-2);
}
.codeblock .cm { color: var(--ink-3); }
.codeblock .hl { color: var(--accent-2); }
.os-build .btn { margin-top: 22px; }

/* ---------- Download ---------- */
.download { background: var(--bg-2); }
.dl-head {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 32px;
  align-items: end;
  margin-bottom: clamp(40px, 7vh, 64px);
}
.dl-head .lead { margin-top: 18px; }
.dl-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 34px;
  padding-top: 22px;
  border-top: 1px solid var(--line-1);
}
.dl-meta div { display: flex; flex-direction: column; gap: 3px; }
.dl-meta dt {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--ink-3);
}
.dl-meta dd { font-size: 0.95rem; font-weight: 600; font-family: var(--font-display); }

.dl-primary {
  display: grid;
  grid-template-columns: minmax(0, 7fr) minmax(0, 5fr);
  gap: 48px;
  align-items: center;
  border: 1px solid var(--line-2);
  border-radius: var(--r-lg);
  background: var(--bg-3);
  padding: clamp(28px, 4vw, 44px);
}
.dl-primary .dl-edition {
  font-family: var(--font-mono);
  font-size: 0.74rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent-3);
}
.dl-primary h3 { font-size: clamp(1.5rem, 2.4vw, 2rem); margin: 12px 0 14px; }
.dl-primary p { color: var(--ink-2); max-width: 52ch; }

.dl-get { display: grid; gap: 14px; }
.dl-get .btn { justify-content: center; width: 100%; }
.dl-get .faint { font-size: 0.82rem; }

.dl-secondary {
  margin-top: 20px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}
.dl-card {
  border: 1px solid var(--line-1);
  border-radius: var(--r-md);
  background: var(--bg-3);
  padding: 26px 28px;
  display: flex;
  flex-direction: column;
}
.dl-card .dl-edition { font-family: var(--font-mono); font-size: 0.74rem; letter-spacing: 0.12em; text-transform: uppercase; color: var(--ink-3); }
.dl-card h4 { font-size: 1.12rem; margin: 10px 0 8px; }
.dl-card p { color: var(--ink-2); font-size: 0.9rem; flex: 1; }
.dl-card .dl-status {
  margin-top: 18px;
  font-family: var(--font-mono);
  font-size: 0.74rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-3);
}

.dl-note {
  margin-top: 28px;
  color: var(--ink-2);
  font-size: 0.9rem;
  max-width: 72ch;
}
.dl-note a { color: var(--accent-2); text-decoration: none; }
.dl-note a:hover { text-decoration: underline; }

.dl-steps {
  margin-top: 44px;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
  list-style: none;
  counter-reset: step;
}
.dl-steps li { border-top: 1px solid var(--line-2); padding-top: 18px; }
.dl-steps li::before {
  counter-increment: step;
  content: counter(step) ".";
  display: block;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--accent-3);
  margin-bottom: 10px;
}
.dl-steps h4 { font-size: 0.98rem; margin-bottom: 6px; }
.dl-steps p { color: var(--ink-2); font-size: 0.88rem; }

/* ---------- Docs & community ---------- */
.paths-split {
  display: grid;
  grid-template-columns: 1fr 1fr;
  border-top: 1px solid var(--line-1);
}
.paths-split > div { padding: 32px 0 8px; }
.paths-split > div + div { padding-left: 48px; border-left: 1px solid var(--line-1); }
.paths-split h3 { font-size: 1.2rem; }
.paths-split p { color: var(--ink-2); font-size: 0.95rem; margin: 10px 0 18px; max-width: 46ch; }
.paths-split a {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  color: var(--accent-2);
  text-decoration: none;
  font-weight: 550;
  font-size: 0.95rem;
}
.paths-split a:hover { color: var(--accent-3); }
.paths-split svg { width: 15px; height: 15px; }

/* ---------- Footer ---------- */
.site-footer {
  border-top: 1px solid var(--line-1);
  background: var(--bg-0);
  padding-block: 64px 40px;
}
.site-footer .wrap { display: grid; gap: 48px; }
.footer-top {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto;
  gap: 32px;
  align-items: start;
}
.footer-brand .brand-name { font-size: 1.1rem; }
.footer-tagline { color: var(--ink-2); margin-top: 12px; font-size: 0.95rem; }
.footer-tagline b { color: var(--ink-1); font-weight: 600; }
.footer-links { display: flex; gap: 40px; flex-wrap: wrap; }
.footer-links .fl-col { display: grid; gap: 10px; }
.footer-links h5 {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-3);
  margin-bottom: 6px;
  font-weight: 500;
}
.footer-links a { color: var(--ink-2); text-decoration: none; font-size: 0.9rem; }
.footer-links a:hover { color: var(--accent-2); }
.footer-bottom {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
  padding-top: 32px;
  border-top: 1px solid var(--line-1);
  color: var(--ink-3);
  font-size: 0.82rem;
}

/* ---------- Lang toggle ---------- */
.lang-toggle {
  position: relative;
  display: inline-flex;
  align-items: center;
  padding: 0;
  border: 1px solid var(--line-2);
  border-radius: 5px;
  background: var(--bg-2);
  cursor: pointer;
  height: 24px;
  overflow: hidden;
  flex-shrink: 0;
}
.lang-opt {
  position: relative;
  z-index: 1;
  padding: 0 10px;
  font: 500 0.68rem/1 var(--font-mono);
  letter-spacing: 0.08em;
  color: var(--ink-3);
  text-transform: uppercase;
  transition: color 0.25s;
  user-select: none;
}
.lang-toggle .lang-opt.active { color: var(--ink-1); }
.lang-toggle::after {
  content: '';
  position: absolute;
  top: 2px;
  left: 2px;
  width: calc(50% - 2px);
  height: calc(100% - 4px);
  border-radius: 3px;
  background: var(--accent-soft);
  transition: transform 0.3s cubic-bezier(.4,0,.2,1);
  pointer-events: none;
}
.lang-toggle.de::after { transform: translateX(calc(100% + 4px)); }
.lang-toggle:hover { border-color: var(--line-3); }
.lang-toggle:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

/* ---------- Lightbox ---------- */
.lightbox {
  position: fixed;
  inset: 0;
  z-index: 90;
  background: rgba(4, 6, 10, 0.92);
  display: none;
  align-items: center;
  justify-content: center;
  padding: 32px;
}
.lightbox.open { display: flex; }
.lightbox figure { max-width: min(1200px, 94vw); }
.lightbox img {
  width: 100%;
  border-radius: var(--r-md);
  border: 1px solid var(--line-2);
}
.lightbox figcaption {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  margin-top: 12px;
  color: var(--ink-2);
  font-size: 0.9rem;
}
.lightbox figcaption span { font-family: var(--font-mono); color: var(--ink-3); }
.lightbox-close {
  position: absolute;
  top: 22px;
  right: 26px;
  width: 46px;
  height: 46px;
  border-radius: 50%;
  border: 1px solid var(--line-2);
  background: rgba(13, 19, 32, 0.8);
  color: var(--ink-1);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: border-color 0.15s ease;
}
.lightbox-close:hover { border-color: var(--accent-2); }
.lightbox-close svg { width: 20px; height: 20px; }

/* ---------- Language dialog ---------- */
.dialog {
  position: fixed;
  inset: 0;
  z-index: 95;
  background: rgba(4, 6, 10, 0.82);
  display: none;
  align-items: center;
  justify-content: center;
  padding: 24px;
}
.dialog.open { display: flex; }
.dialog-card {
  width: min(440px, 100%);
  background: var(--bg-3);
  border: 1px solid var(--line-2);
  border-radius: var(--r-lg);
  padding: 34px;
}
.dialog-card h2 { font-size: 1.2rem; margin-bottom: 6px; }
.dialog-card > p { color: var(--ink-2); font-size: 0.9rem; margin-bottom: 22px; }
.dl-opt {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  width: 100%;
  padding: 15px 18px;
  margin-bottom: 10px;
  background: var(--bg-2);
  border: 1px solid var(--line-1);
  border-radius: var(--r-sm);
  color: var(--ink-1);
  font-size: 0.98rem;
  font-weight: 550;
  cursor: pointer;
  transition: border-color 0.15s ease, background-color 0.15s ease;
}
.dl-opt:hover { border-color: var(--line-3); }
.dl-opt[aria-pressed="true"] { border-color: var(--accent); background: var(--accent-soft); }
.dl-opt .l-lang { font-family: var(--font-mono); font-size: 0.74rem; color: var(--ink-3); text-transform: uppercase; letter-spacing: 0.1em; }
.dialog-actions { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 20px; }

/* ---------- Responsive ---------- */
@media (max-width: 1024px) {
  .split, .split-wide, .schools-grid, .os-grid, .spec-grid { grid-template-columns: minmax(0, 1fr); gap: 44px; }
  .schools-aside, .spec-intro, .principles .split-lead { position: static; }
  .exp-bar { gap: 0; margin-bottom: 28px; }
  .exp-tab { padding: 12px 14px; min-width: 120px; }
  .ep-grid { grid-template-columns: 1fr; }
  .ep-apps { grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 20px 12px; }
  .ep-app img { width: 42px; height: 42px; }
  .dl-head { grid-template-columns: minmax(0, 1fr); gap: 24px; }
  .dl-primary { grid-template-columns: minmax(0, 1fr); gap: 28px; }
  .dl-steps { grid-template-columns: minmax(0, 1fr); gap: 26px; }
}

@media (max-width: 720px) {
  .site-nav, .site-nav .nav-cta { display: none; }
  .nav-toggle { display: inline-flex; }
  .problem-list { grid-template-columns: 1fr; gap: 0 0; }
  .schools-points { grid-template-columns: 1fr; }
  .os-verbs { grid-template-columns: 1fr; }
  .dl-secondary { grid-template-columns: 1fr; }
  .paths-split { grid-template-columns: 1fr; }
  .paths-split > div + div { padding-left: 0; border-left: none; border-top: 1px solid var(--line-1); }
  .exp-tools div { grid-template-columns: 1fr; gap: 2px; }
  .footer-top { grid-template-columns: 1fr; }
  .footer-links { gap: 28px; }
  .principle-head {
    grid-template-columns: minmax(0, 1fr) 20px;
    gap: 8px 16px;
    padding-block: 20px;
  }
  .principle-head .ph-summary { grid-column: 1 / -1; }
  .req-table th { padding: 0 14px 10px 0; }
  .req-table td { padding: 14px 14px 14px 0; font-size: 0.9rem; }
  .spec-limits { margin-top: 30px; padding-top: 24px; }
  .ep-head h3 { font-size: 1.2rem; }
  .ep-head p { max-width: none; }
}

@media (max-width: 460px) {
  .display { font-size: clamp(2.1rem, 9vw, 2.6rem); }
  .dl-steps li { padding-top: 14px; }
}

/* ---------- Reduced motion ---------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}