/* ==========================================================================
   Naser Academy — "Glow" app shell (light theme)
   Glass panels with lit edges, an icon rail, course tabs, a perspective grid.
   ========================================================================== */
:root {
  --paper: #f3f6fb;
  --surface: #ffffff;
  --surface-2: #f6f8fc;
  --sunken: #eef2f8;
  --ink: #0b1324;
  --ink-2: #2b3852;
  --muted: #5a6680;
  --rule: #dfe5ef;
  --rule-strong: #c8d1e0;
  --signal: #0e7490;
  --signal-ink: #ffffff;
  --blue: #2563eb;
  --ok: #047857;
  --ok-soft: #e3f5ec;
  --bad: #b91c1c;
  --bad-soft: #fdecec;
  --flame: #c2410c;
  --pink: #db2777;
  --glass: linear-gradient(180deg, #ffffff, #f8fafd);
  --grid-line: rgba(37, 99, 235, .08);
  --shadow: 0 24px 48px -28px rgba(15, 30, 60, .35);
  --card-stock: #e9dec0; --card-ink: #26282e; --card-hole: #1c2a4a;
  --font: "IBM Plex Sans Arabic", "Segoe UI", Tahoma, sans-serif;
  --display: "Cairo", "IBM Plex Sans Arabic", sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, Consolas, monospace;
  --rail-w: 84px;
  --top-h: 60px;
  --ease: cubic-bezier(.2, .7, .2, 1);
  color-scheme: light;
}
/* course colour: --c set inline from courses.js; --ct is its readable text tone */
* { --ct: color-mix(in oklab, var(--c, var(--signal)) 72%, black); }

/* ---------- base ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-padding-top: calc(var(--top-h) + 16px); }
body {
  margin: 0; min-height: 100vh; color: var(--ink); font-family: var(--font); font-size: 16.5px; line-height: 1.75;
  background: radial-gradient(900px 500px at 70% -10%, rgba(37, 99, 235, .08), transparent 60%), var(--paper);
  background-attachment: fixed;
  -webkit-font-smoothing: antialiased;
}
img, svg { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; }
h1, h2, h3, h4 { font-family: var(--display); font-weight: 700; line-height: 1.35; margin: 0; }
p { margin: 0; }
bdi, .ltr { unicode-bidi: isolate; }
.ltr { direction: ltr; }
code, kbd, pre, .mono { font-family: var(--mono); font-variant-ligatures: none; }
:focus-visible { outline: 2px solid var(--signal); outline-offset: 2px; border-radius: 6px; }
::selection { background: rgba(34, 211, 238, .3); }
.container { width: 100%; max-width: 1220px; margin: 0 auto; padding: 0 16px; }
@media (min-width: 768px) { .container { padding: 0 32px; } }
.sr-only { position: absolute !important; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; }
.skip { position: absolute; top: -48px; inset-inline-start: 12px; z-index: 100; background: var(--signal); color: var(--signal-ink); padding: 8px 14px; border-radius: 8px; }
.skip:focus { top: 12px; }
[hidden] { display: none !important; }
.muted { color: var(--muted); }

.i { width: 20px; height: 20px; flex: none; stroke: currentColor; fill: none; stroke-width: 1.8; stroke-linecap: round; stroke-linejoin: round; }
.i-sm { width: 16px; height: 16px; }
.i-lg { width: 26px; height: 26px; }

/* ---------- glass panels with lit edges ---------- */
.glow {
  --g: var(--c, var(--blue));
  position: relative; background: var(--glass); border-radius: 18px;
  border: 1.5px solid color-mix(in srgb, var(--g) 70%, transparent);
  box-shadow: 0 0 0 1px rgba(255, 255, 255, .03) inset, 0 0 28px -6px color-mix(in srgb, var(--g) 55%, transparent), var(--shadow);
}
.glow { border-color: color-mix(in srgb, var(--g) 45%, transparent); box-shadow: 0 0 22px -10px color-mix(in srgb, var(--g) 60%, transparent), var(--shadow); }
.card { background: var(--surface); border: 1px solid var(--rule); border-radius: 14px; }

/* ---------- buttons ---------- */
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 8px; min-height: 44px; padding: 0 18px; border-radius: 10px; border: 1.5px solid transparent; font-weight: 600; font-size: 15.5px; cursor: pointer; white-space: nowrap; transition: background-color .15s, border-color .15s, color .15s, box-shadow .2s; }
.btn-primary { background: var(--signal); color: var(--signal-ink); box-shadow: 0 0 22px -6px rgba(34, 211, 238, .7); }
.btn-primary:hover { background: color-mix(in srgb, var(--signal) 85%, white); }
.btn-primary { box-shadow: none; }
.btn-primary:hover { background: color-mix(in srgb, var(--signal) 85%, black); }
.btn-outline { background: transparent; border-color: var(--rule-strong); color: var(--ink); }
.btn-outline:hover { border-color: var(--signal); color: var(--signal); }
.btn-ghost { background: transparent; color: var(--ink-2); }
.btn-ghost:hover { background: var(--surface-2); color: var(--ink); }
.btn-sm { min-height: 36px; padding: 0 12px; font-size: 14.5px; }
.btn[disabled], .btn[aria-disabled="true"] { opacity: .45; pointer-events: none; }
.icon-btn { width: 40px; height: 40px; display: inline-grid; place-items: center; flex: none; border-radius: 10px; border: 0; background: transparent; color: var(--ink-2); cursor: pointer; transition: background-color .15s, color .15s; }
.icon-btn:hover { background: var(--surface-2); color: var(--ink); }
.icon-btn[aria-pressed="true"] { color: var(--signal); }

/* ---------- app shell: rail + top bar ---------- */
.rail { position: fixed; z-index: 60; top: 0; bottom: 0; inset-inline-start: 0; width: var(--rail-w); display: flex; flex-direction: column; align-items: center; gap: 6px; padding: 14px 0; background: color-mix(in srgb, var(--paper) 88%, transparent); border-inline-end: 1px solid var(--rule); backdrop-filter: blur(10px); }
.rail-logo { margin-bottom: 14px; }
.rail-logo .logo { width: 38px; height: 38px; }
.rail-items { display: flex; flex-direction: column; gap: 4px; width: 100%; padding: 0 10px; }
.rail-items a { position: relative; display: flex; flex-direction: column; align-items: center; gap: 2px; padding: 10px 0 8px; border-radius: 12px; color: var(--muted); font-size: 12px; font-weight: 600; transition: color .15s, background-color .15s; }
.rail-items a .i { width: 22px; height: 22px; }
.rail-items a:hover { color: var(--ink); background: var(--surface-2); }
.rail-items a[aria-current="page"] { color: var(--ink); background: linear-gradient(180deg, rgba(59, 130, 246, .28), rgba(59, 130, 246, .10)); box-shadow: inset 0 0 0 1px rgba(59, 130, 246, .45); }
.rail-items a[aria-current="page"]::before { content: ""; position: absolute; inset-inline-start: -10px; top: 10px; bottom: 10px; width: 3px; border-radius: 3px; background: var(--blue); box-shadow: 0 0 12px var(--blue); }
.rail-items a[aria-current="page"] { background: rgba(37, 99, 235, .1); }
.rail-bottom { margin-top: auto; }
body.has-rail { padding-inline-start: var(--rail-w); }

.topbar { position: sticky; top: 0; z-index: 50; height: var(--top-h); display: flex; align-items: center; gap: 16px; padding: 0 16px; background: color-mix(in srgb, var(--paper) 86%, transparent); backdrop-filter: blur(10px); border-bottom: 1px solid var(--rule); }
.tabbar { display: flex; align-items: flex-end; gap: 4px; height: 100%; overflow-x: auto; scrollbar-width: none; flex: 1; min-width: 0; padding-top: 10px; }
.tab { display: inline-flex; align-items: center; gap: 8px; height: 100%; padding: 0 16px; border-radius: 10px 10px 0 0; color: var(--muted); font-size: 14.5px; font-weight: 600; white-space: nowrap; border: 1px solid transparent; border-bottom: 0; }
.tab:hover { color: var(--ink); }
.tab.on { color: var(--ink); background: var(--surface); border-color: var(--rule); box-shadow: inset 0 2px 0 var(--ct); }
.tab .dot { width: 8px; height: 8px; border-radius: 50%; background: var(--ct); box-shadow: 0 0 8px var(--ct); }
.tab-home .logo { display: none; width: 24px; height: 24px; flex: none; }
.top-actions { display: flex; align-items: center; gap: 6px; }
.search-trigger { display: inline-flex; align-items: center; gap: 10px; height: 40px; min-width: 280px; padding: 0 12px; border: 1px solid var(--rule-strong); background: var(--sunken); color: var(--muted); border-radius: 10px; cursor: pointer; }
.search-trigger:hover { border-color: var(--signal); }
.search-trigger span { flex: 1; text-align: start; font-size: 14.5px; }
kbd { font-size: 11.5px; padding: 1px 6px; border-radius: 5px; border: 1px solid var(--rule-strong); color: var(--muted); direction: ltr; }
@media (max-width: 1080px) { .search-trigger { min-width: 0; width: 40px; padding: 0; justify-content: center; } .search-trigger span, .search-trigger kbd { display: none; } }
@media (max-width: 860px) {
  body.has-rail { padding-inline-start: 0; padding-bottom: 72px; }
  .rail { top: auto; bottom: 0; inset-inline: 0; width: auto; height: 68px; flex-direction: row; padding: 0 6px; border-inline-end: 0; border-top: 1px solid var(--rule); }
  .rail-logo, .rail-bottom { display: none; }
  .rail-items { flex-direction: row; justify-content: space-around; padding: 0; }
  .rail-items a { flex: 1; padding: 8px 0 6px; }
  .rail-items a[aria-current="page"]::before { inset-inline-start: 20%; inset-inline-end: 20%; top: -1px; bottom: auto; width: auto; height: 3px; }
  .tab-home .logo { display: block; }
  .tab-home .i, .tab-home span { display: none; }
  .tab { padding: 0 9px; font-size: 13.5px; gap: 6px; }
  .tab .dot { width: 6px; height: 6px; }
  .topbar { gap: 8px; padding: 0 10px; }
}

/* ---------- footer ---------- */
.site-footer { margin-top: 96px; border-top: 1px solid var(--rule); }
.ftr { display: grid; gap: 28px; grid-template-columns: 1.6fr repeat(3, 1fr); padding-top: 40px; padding-bottom: 28px; }
.ftr h4 { font-family: var(--font); font-size: 14.5px; color: var(--muted); font-weight: 600; margin-bottom: 8px; }
.ftr ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 4px; }
.ftr ul a { color: var(--ink-2); font-size: 15px; }
.ftr ul a:hover { color: var(--signal); }
.ftr p { color: var(--muted); font-size: 14.5px; margin-top: 10px; max-width: 34ch; }
.ftr .brand { display: inline-flex; align-items: center; gap: 10px; font-family: var(--display); font-weight: 700; direction: ltr; }
.ftr .brand .logo { width: 30px; height: 30px; }
.ftr-bottom { border-top: 1px solid var(--rule); padding-top: 16px; padding-bottom: 24px; display: flex; flex-wrap: wrap; gap: 8px 24px; justify-content: space-between; color: var(--muted); font-size: 13.5px; }
@media (max-width: 760px) { .ftr { grid-template-columns: 1fr 1fr; } .ftr > :first-child { grid-column: 1 / -1; } }

/* ---------- shared pieces ---------- */
.section { padding-top: 88px; }
.section-head { display: flex; align-items: flex-end; justify-content: space-between; gap: 16px; margin-bottom: 26px; flex-wrap: wrap; }
.section-head h2 { font-size: clamp(24px, 3vw, 32px); }
.section-head p { color: var(--muted); margin-top: 6px; max-width: 62ch; }
.eyebrow { display: none; }
.link-more { display: inline-flex; align-items: center; gap: 6px; color: var(--signal); font-weight: 600; font-size: 15px; }
.link-more:hover { text-decoration: underline; text-underline-offset: 5px; }
.badge { display: inline-flex; align-items: center; gap: 6px; padding: 1px 10px; border-radius: 999px; font-size: 13px; font-weight: 600; background: var(--surface-2); color: var(--ink-2); white-space: nowrap; line-height: 1.7; border: 1px solid var(--rule); }
.badge-c { background: color-mix(in srgb, var(--ct) 14%, transparent); color: var(--ct); border-color: color-mix(in srgb, var(--ct) 35%, transparent); }
.badge-ok { background: var(--ok-soft); color: var(--ok); border-color: transparent; }
.badge-soon { background: transparent; color: var(--muted); }
.progress { height: 6px; border-radius: 6px; background: var(--rule); overflow: hidden; }
.progress > i { display: block; height: 100%; width: 0; border-radius: inherit; background: linear-gradient(90deg, var(--ct), color-mix(in srgb, var(--ct) 60%, white)); box-shadow: 0 0 10px var(--ct); transition: width .6s var(--ease); }
[dir="rtl"] .progress > i { background: linear-gradient(270deg, var(--ct), color-mix(in srgb, var(--ct) 60%, white)); }
.grid { display: grid; gap: 18px; }
.grid > * { min-width: 0; }
.empty-state { text-align: center; padding: 40px 20px; border: 1.5px dashed var(--rule-strong); border-radius: 16px; color: var(--muted); }
.empty-state h3 { color: var(--ink); font-size: 19px; margin: 10px 0 4px; }
.empty-state .i-lg { margin: 0 auto; }
.chips { display: flex; flex-wrap: wrap; gap: 8px; }
.chip { display: inline-flex; align-items: center; gap: 8px; min-height: 36px; padding: 0 14px; border-radius: 999px; border: 1px solid var(--rule-strong); background: var(--surface); color: var(--ink-2); font-size: 14.5px; cursor: pointer; }
.chip:hover { border-color: var(--signal); }
.chip[aria-pressed="true"] { background: var(--signal); border-color: var(--signal); color: var(--signal-ink); }
.chip .n { font-size: 12.5px; opacity: .75; }
.chip .dot { width: 8px; height: 8px; border-radius: 50%; background: var(--ct); }
.reveal { opacity: 1; }
mark { background: rgba(34, 211, 238, .25); color: inherit; border-radius: 3px; padding: 0 2px; }

pre.code { direction: ltr; text-align: left; margin: 0; padding: 14px 16px; overflow-x: auto; background: var(--sunken); border: 1px solid var(--rule); border-radius: 10px; font-size: 14px; line-height: 1.7; color: var(--ink); }
pre.code .k { color: #7dd3fc; font-weight: 600; }
pre.code .s { color: #fdba74; }
pre.code .n { color: #6ee7b7; }
pre.code .c { color: var(--muted); font-style: italic; }
pre.code .f { color: #c4b5fd; }
pre.code .k { color: #1d4ed8; }
pre.code .s { color: #b45309; }
pre.code .n { color: #047857; }
pre.code .f { color: #6d28d9; }

.toasts { position: fixed; z-index: 200; inset-inline: 0; bottom: 88px; display: grid; justify-items: center; gap: 8px; pointer-events: none; padding: 0 16px; }
@media (min-width: 861px) { .toasts { bottom: 24px; } }
.toast { pointer-events: auto; display: flex; align-items: center; gap: 12px; max-width: 520px; background: var(--surface-2); color: var(--ink); border: 1px solid var(--rule-strong); padding: 10px 12px 10px 16px; border-radius: 12px; font-size: 15px; box-shadow: var(--shadow); animation: toastIn .25s var(--ease); }
.toast button { background: transparent; color: var(--signal); border: 1px solid currentColor; border-radius: 8px; padding: 4px 10px; font-weight: 600; cursor: pointer; white-space: nowrap; }
.toast.out { animation: toastOut .2s var(--ease) forwards; }
@keyframes toastIn { from { opacity: 0; transform: translateY(8px); } }
@keyframes toastOut { to { opacity: 0; transform: translateY(6px); } }

.palette-backdrop { position: fixed; inset: 0; z-index: 150; background: rgba(3, 7, 18, .6); backdrop-filter: blur(4px); display: grid; align-items: start; justify-items: center; padding: 10vh 16px 16px; animation: fade .15s ease; }
.palette { width: 100%; max-width: 640px; background: var(--surface); border: 1.5px solid rgba(59, 130, 246, .55); border-radius: 16px; overflow: hidden; box-shadow: 0 0 40px -10px rgba(59, 130, 246, .5), var(--shadow); animation: drop .18s var(--ease); }
.palette-input { display: flex; align-items: center; gap: 10px; padding: 0 16px; border-bottom: 1px solid var(--rule); color: var(--muted); }
.palette-input input { flex: 1; height: 58px; border: 0; outline: 0; background: transparent; color: var(--ink); font: inherit; font-size: 17px; }
.palette-results { max-height: min(60vh, 460px); overflow-y: auto; padding: 6px; }
.palette-group { font-size: 13px; color: var(--muted); padding: 10px 10px 2px; }
.palette-item { display: flex; align-items: center; gap: 12px; padding: 10px; border-radius: 10px; cursor: pointer; }
.palette-item .ico { width: 34px; height: 34px; border-radius: 9px; display: grid; place-items: center; flex: none; color: var(--ct); background: color-mix(in srgb, var(--ct) 14%, transparent); }
.palette-item .t { font-weight: 600; font-size: 15.5px; }
.palette-item .d { font-size: 13.5px; color: var(--muted); display: -webkit-box; -webkit-line-clamp: 1; -webkit-box-orient: vertical; overflow: hidden; }
.palette-item[aria-selected="true"] { background: var(--surface-2); box-shadow: inset 0 0 0 1px var(--rule-strong); }
.palette-foot { display: flex; justify-content: space-between; gap: 12px; padding: 10px 16px; border-top: 1px solid var(--rule); font-size: 13.5px; color: var(--muted); }
.palette-foot a { color: var(--signal); font-weight: 600; }
@keyframes fade { from { opacity: 0; } }
@keyframes drop { from { opacity: 0; transform: translateY(-6px); } }

/* ==========================================================================
   HOME — the panel stage
   ========================================================================== */
.stage { position: relative; padding: 48px 0 0; overflow: hidden; }
.stage::after { /* perspective grid floor */
  content: ""; position: absolute; inset: auto -20% -10% -20%; height: 360px; z-index: -1; pointer-events: none;
  background-image: linear-gradient(var(--grid-line) 1px, transparent 1px), linear-gradient(90deg, var(--grid-line) 1px, transparent 1px);
  background-size: 56px 56px; transform: perspective(500px) rotateX(62deg); transform-origin: bottom;
  mask-image: linear-gradient(to top, #000 10%, transparent 85%); -webkit-mask-image: linear-gradient(to top, #000 10%, transparent 85%);
}
.panels { display: grid; grid-template-columns: 1fr 1.08fr 1fr; gap: 26px; align-items: center; perspective: 1400px; }
.panel { padding: 24px 22px 22px; min-width: 0; }
.panel:nth-child(1) { --g: #3b82f6; transform: rotateY(-9deg) translateZ(-10px); }
.panel:nth-child(2) { --g: #22d3ee; transform: translateY(-14px); z-index: 2; }
.panel:nth-child(3) { --g: #38bdf8; transform: rotateY(9deg) translateZ(-10px); }
.panel-head { display: flex; align-items: flex-start; justify-content: space-between; gap: 12px; margin-bottom: 18px; }
.panel-ico { width: 40px; height: 40px; border-radius: 10px; display: grid; place-items: center; color: var(--g); border: 1.5px solid color-mix(in srgb, var(--g) 60%, transparent); background: color-mix(in srgb, var(--g) 12%, transparent); flex: none; }
.panel h2 { font-size: 26px; line-height: 1.3; }
.panel .sub { color: var(--muted); font-size: 14.5px; margin-top: 6px; }
.panel .tag { font-family: var(--font); font-size: 13.5px; font-weight: 600; color: var(--g); border: 1px solid color-mix(in srgb, var(--g) 55%, transparent); border-radius: 8px; padding: 2px 9px; white-space: nowrap; }
/* steps list */
.steps { list-style: none; margin: 0; padding: 0; display: grid; gap: 10px; position: relative; }
.steps::before { content: ""; position: absolute; inset-inline-start: 6px; top: 18px; bottom: 18px; width: 2px; background: color-mix(in srgb, var(--blue) 55%, transparent); }
.steps li { display: flex; align-items: center; gap: 12px; }
.steps .node { width: 14px; height: 14px; border-radius: 50%; background: var(--paper); border: 3px solid var(--blue); flex: none; position: relative; z-index: 1; box-shadow: 0 0 8px var(--blue); }
.steps a { flex: 1; display: flex; align-items: center; gap: 12px; padding: 10px 12px; border-radius: 10px; background: var(--surface-2); border: 1px solid var(--rule); transition: border-color .15s; min-width: 0; }
.steps a:hover { border-color: var(--ct); }
.steps .num { font-family: var(--mono); font-size: 13px; font-weight: 600; color: var(--ct); border: 1px solid color-mix(in srgb, var(--ct) 50%, transparent); border-radius: 7px; padding: 1px 7px; }
.steps .name { flex: 1; font-weight: 600; direction: ltr; text-align: right; }
.steps .meta { font-size: 13px; color: var(--muted); white-space: nowrap; }
.steps .check { width: 22px; height: 22px; border-radius: 50%; display: grid; place-items: center; flex: none; border: 2px solid var(--rule-strong); color: transparent; }
.steps .check.on { background: var(--blue); border-color: var(--blue); color: #fff; }
.mini-progress { display: flex; align-items: center; gap: 12px; margin-top: 16px; padding: 12px 14px; border-radius: 12px; background: var(--surface-2); border: 1px solid var(--rule); }
.mini-progress .ico { width: 34px; height: 34px; border-radius: 50%; display: grid; place-items: center; background: color-mix(in srgb, var(--blue) 18%, transparent); color: var(--blue); flex: none; }
.mini-progress .body { flex: 1; min-width: 0; }
.mini-progress .row { display: flex; justify-content: space-between; font-size: 14px; color: var(--ink-2); margin-bottom: 6px; }
.mini-progress .row b { color: var(--blue); font-family: var(--mono); }
.mini-progress .progress > i { --ct: var(--blue); }
/* practice panel */
.run { display: flex; align-items: center; gap: 18px; padding: 16px; border-radius: 14px; background: var(--surface-2); border: 1px solid var(--rule); margin-bottom: 14px; }
.run-btn { width: 84px; height: 84px; border-radius: 50%; display: grid; place-items: center; flex: none; border: 3px solid var(--signal); color: var(--signal); background: radial-gradient(circle, rgba(34, 211, 238, .12), transparent 70%); box-shadow: 0 0 24px -4px rgba(34, 211, 238, .7), inset 0 0 18px -6px rgba(34, 211, 238, .8); transition: transform .2s var(--ease); }
.run-btn .i { width: 34px; height: 34px; fill: currentColor; stroke: none; }
.run-btn:hover { transform: scale(1.05); }
.run h3 { font-size: 20px; }
.run p { color: var(--muted); font-size: 14px; }
.streak { display: inline-flex; align-items: center; gap: 6px; margin-top: 8px; padding: 3px 10px; border-radius: 8px; font-size: 13.5px; font-weight: 600; color: var(--flame); background: color-mix(in srgb, var(--flame) 14%, transparent); border: 1px solid color-mix(in srgb, var(--flame) 55%, transparent); }
.skills { list-style: none; margin: 0; padding: 4px 14px; border-radius: 14px; background: var(--surface-2); border: 1px solid var(--rule); }
.skills li { display: grid; grid-template-columns: 22px 64px 1fr 40px; align-items: center; gap: 10px; padding: 10px 0; font-size: 14px; }
.skills li + li { border-top: 1px solid var(--rule); }
.skills .i { color: var(--ct); }
.skills .lbl { direction: ltr; text-align: right; font-weight: 600; }
.skills .pct { font-family: var(--mono); font-size: 12.5px; color: var(--muted); text-align: end; }
/* references panel */
.magnifier { color: var(--g); flex: none; filter: drop-shadow(0 0 10px color-mix(in srgb, var(--g) 60%, transparent)); }
.refs { list-style: none; margin: 0 0 14px; padding: 0; border-radius: 14px; overflow: hidden; border: 1px solid var(--rule); background: var(--surface-2); }
.refs li + li { border-top: 1px solid var(--rule); }
.refs a { display: flex; align-items: center; gap: 12px; padding: 11px 14px; font-size: 14.5px; }
.refs a:hover { background: var(--sunken); }
.refs .i { color: var(--g); }
.refs .t { flex: 1; min-width: 0; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.refs .chev { color: var(--muted); }
.snippet { position: relative; border-radius: 14px; border: 1px solid var(--rule); background: var(--sunken); padding: 40px 14px 12px; }
.snippet .lang { position: absolute; top: 10px; right: 12px; left: auto; font-family: var(--mono); font-size: 11.5px; font-weight: 600; color: var(--g); border: 1px solid color-mix(in srgb, var(--g) 50%, transparent); border-radius: 6px; padding: 0 6px; }
.snippet pre { margin: 0; direction: ltr; text-align: left; font-family: var(--mono); font-size: 12px; line-height: 1.8; color: var(--ink-2); overflow-x: auto; white-space: pre; scrollbar-width: thin; }
.snippet pre .ln { color: var(--muted); opacity: .6; margin-right: 10px; }
.snippet pre .k { color: #7dd3fc; font-weight: 600; }
.snippet pre .k { color: #1d4ed8; }
.snippet .copy { position: absolute; top: 4px; left: 6px; width: 32px; height: 32px; }
/* title pill */
.title-pill { display: flex; justify-content: center; margin-top: 46px; }
.title-pill h1 { display: inline-flex; align-items: center; gap: 12px; padding: 12px 22px; border-radius: 14px; font-size: clamp(20px, 2.6vw, 28px); font-weight: 700; text-align: center; }
.title-pill h1 .i { color: var(--blue); width: 26px; height: 26px; }
.title-pill h1 .heart { color: var(--pink); fill: var(--pink); stroke: none; width: 22px; height: 22px; }
.stage-cta { display: flex; justify-content: center; flex-wrap: wrap; gap: 10px; margin-top: 22px; padding-bottom: 40px; }
.stage-lead { text-align: center; color: var(--ink-2); max-width: 62ch; margin: 14px auto 0; }
@media (max-width: 1080px) {
  .panels { grid-template-columns: 1fr 1fr; }
  .panel:nth-child(1), .panel:nth-child(2), .panel:nth-child(3) { transform: none; }
  .panel:nth-child(2) { grid-column: 1 / -1; order: -1; }
}
@media (max-width: 680px) {
  .panels { grid-template-columns: 1fr; }
  .title-pill h1 { flex-wrap: wrap; justify-content: center; }
  .stage > .container { display: flex; flex-direction: column; }
  .stage .title-pill { order: -3; margin-top: 0; }
  .stage .stage-lead { order: -2; }
  .stage .stage-cta { order: -1; padding-bottom: 32px; }
}

/* course cards */
.course-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 24px; }
.ccard { display: flex; flex-direction: column; overflow: hidden; transition: transform .2s var(--ease), box-shadow .2s; --g: var(--c); }
.ccard:hover { transform: translateY(-4px); }
.ccard .cover { display: block; aspect-ratio: 16 / 9; border-bottom: 1px solid var(--rule); }
.ccard .cover svg { width: 100%; height: 100%; }
.cover-art { direction: ltr; }
.ccard .body { padding: 18px 20px 20px; display: flex; flex-direction: column; gap: 10px; flex: 1; }
.ccard h3 { font-size: 24px; direction: ltr; text-align: right; }
.ccard h3 a:hover { color: var(--ct); }
.ccard .sub { color: var(--muted); font-size: 14px; margin-top: -6px; }
.ccard p { color: var(--ink-2); font-size: 15px; }
.ccard .stats { display: flex; flex-wrap: wrap; gap: 6px; }
.ccard .foot { margin-top: auto; display: grid; gap: 12px; padding-top: 6px; }
.ccard .prog-row { display: flex; justify-content: space-between; font-size: 13.5px; color: var(--muted); }
.ccard .btn { width: 100%; }

/* newest lesson */
.latest { display: grid; grid-template-columns: 1.1fr 1fr; gap: 40px; align-items: center; padding: 28px; }
.latest > * { min-width: 0; }
.latest-pages { position: relative; padding-bottom: 20%; }
.latest-pages .page { display: block; border-radius: 12px; overflow: hidden; border: 1px solid var(--rule-strong); }
.latest-pages img { width: 100%; height: auto; display: block; }
.latest-pages .page-cover { width: 88%; }
.latest-pages .page-preview { position: absolute; width: 78%; inset-inline-end: 0; bottom: 0; box-shadow: 0 24px 40px -18px rgba(0, 0, 0, .7); }
.latest-text .kicker { display: inline-flex; margin-bottom: 10px; }
.latest-text h2 { font-size: clamp(26px, 3vw, 34px); direction: ltr; text-align: right; }
.latest-text h2 a:hover { color: var(--ct); }
.latest-text > p { color: var(--ink-2); margin-top: 10px; }
.latest-parts { list-style: none; padding: 0; margin: 16px 0 22px; display: grid; gap: 8px; }
.latest-parts a { display: flex; align-items: center; gap: 10px; color: var(--ink-2); font-size: 15px; }
.latest-parts a .i { color: var(--ct); }
.latest-parts a:hover { color: var(--ink); }
@media (max-width: 880px) { .latest { grid-template-columns: 1fr; gap: 26px; padding: 20px; } }

/* try-a-question */
.tryq { display: grid; grid-template-columns: 1fr 1.25fr; gap: 40px; align-items: center; padding: 28px; --g: var(--signal); }
.tryq > * { min-width: 0; }
.tryq .intro h2 { font-size: clamp(24px, 3vw, 30px); }
.tryq .intro p { color: var(--ink-2); margin-top: 10px; }
.tryq .intro ul { list-style: none; padding: 0; margin: 20px 0 0; display: grid; gap: 10px; }
.tryq .intro li a { font-weight: 600; color: var(--signal); }
.tryq .intro li span { color: var(--muted); }
.qcard { padding: 20px; background: var(--surface-2); border: 1px solid var(--rule); border-radius: 14px; }
.qcard .meta { display: flex; justify-content: space-between; align-items: center; gap: 12px; margin-bottom: 10px; font-size: 14px; color: var(--muted); }
.qcard h3 { font-family: var(--font); font-size: 18.5px; font-weight: 600; line-height: 1.6; margin-bottom: 14px; }
.qcard pre.code { margin-bottom: 14px; }
@media (max-width: 880px) { .tryq { grid-template-columns: 1fr; gap: 22px; padding: 20px; } }

/* lesson cards (search, me) */
.lessons-grid { grid-template-columns: repeat(auto-fill, minmax(290px, 1fr)); }
.lesson-card { display: flex; flex-direction: column; gap: 8px; padding: 0; position: relative; overflow: hidden; }
.lesson-card .thumb { display: block; aspect-ratio: 16 / 7; overflow: hidden; border-bottom: 1px solid var(--rule); background: var(--sunken); }
.lesson-card .thumb img, .lesson-card .thumb svg { width: 100%; height: 100%; object-fit: cover; object-position: center top; }
.lesson-card .inner { padding: 14px 18px 16px; display: flex; flex-direction: column; gap: 8px; flex: 1; }
.lesson-card .row { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.lesson-card h3 { font-size: 18px; }
.lesson-card h3 a:hover { color: var(--ct); }
.lesson-card p { color: var(--muted); font-size: 14.5px; display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.lesson-card .foot { display: flex; align-items: center; justify-content: space-between; gap: 8px; margin-top: auto; padding-top: 8px; font-size: 13.5px; color: var(--muted); }
.lesson-card .bm { position: absolute; top: 8px; inset-inline-end: 8px; background: color-mix(in srgb, var(--paper) 70%, transparent); backdrop-filter: blur(6px); }
.continue-card { display: flex; align-items: center; gap: 14px; padding: 14px 18px; border-inline-start: 3px solid var(--ct); }
.continue-card .ico { color: var(--ct); }
.continue-card .t { font-weight: 700; }
.continue-card .s { font-size: 13.5px; color: var(--muted); }
.continue-card .go { display: none; }

/* ==========================================================================
   COURSE PAGE
   ========================================================================== */
.course-hero { padding: 32px 0 36px; }
.crumbs { display: flex; align-items: center; flex-wrap: wrap; gap: 6px; color: var(--muted); font-size: 14.5px; margin-bottom: 18px; }
.crumbs a:hover { color: var(--signal); }
.course-hero .inner { display: grid; grid-template-columns: 1fr 380px; gap: 40px; align-items: center; padding: 28px; --g: var(--c); }
.course-hero .inner > * { min-width: 0; }
.course-hero h1 { font-size: clamp(32px, 4.4vw, 46px); direction: ltr; text-align: right; line-height: 1.2; }
.course-hero .sub { color: var(--muted); }
.course-hero p.desc { color: var(--ink-2); margin-top: 14px; max-width: 62ch; font-size: 17px; }
.course-hero .actions { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 22px; }
.course-progress { display: grid; gap: 10px; font-size: 14.5px; color: var(--ink-2); }
.course-progress .course-card { border-radius: 14px; overflow: hidden; border: 1px solid var(--rule-strong); aspect-ratio: 16 / 9; margin-bottom: 6px; }
.course-progress .course-card svg { width: 100%; height: 100%; }
.course-progress b { font-family: var(--display); font-size: 26px; color: var(--ink); }
.course-stats { display: flex; flex-wrap: wrap; gap: 4px 16px; color: var(--muted); font-size: 14px; }
@media (max-width: 860px) { .course-hero .inner { grid-template-columns: 1fr; padding: 20px; } .course-progress { order: -1; } }

.course-body { display: grid; grid-template-columns: 250px 1fr; gap: 40px; padding-top: 8px; align-items: start; }
.course-body > * { min-width: 0; }
.toc { position: sticky; top: calc(var(--top-h) + 20px); padding: 16px; }
.toc h4 { font-family: var(--font); font-size: 14px; color: var(--muted); margin: 0 0 8px; font-weight: 600; }
.toc a { display: flex; align-items: center; gap: 8px; padding: 6px 8px; border-radius: 8px; font-size: 14.5px; color: var(--ink-2); direction: ltr; justify-content: flex-end; }
.toc a:hover { background: var(--surface-2); color: var(--ink); }
.toc a.is-empty { color: var(--muted); }
.toc a .n { order: -1; margin-inline-end: auto; font-size: 12.5px; color: var(--ct); font-weight: 700; }
.toc a.is-empty .n { color: var(--muted); font-weight: 400; }
.toc label { display: flex; align-items: center; gap: 8px; font-size: 14px; color: var(--muted); padding-top: 12px; margin-top: 10px; border-top: 1px solid var(--rule); cursor: pointer; }
@media (max-width: 900px) { .course-body { grid-template-columns: 1fr; } .toc { display: none; } }

.cat-block { margin-bottom: 12px; scroll-margin-top: calc(var(--top-h) + 16px); background: var(--surface); border: 1px solid var(--rule); border-radius: 14px; overflow: hidden; }
.cat-head { display: flex; align-items: center; gap: 14px; padding: 14px 18px; }
.cat-num { font-family: var(--mono); font-weight: 600; font-size: 13px; color: var(--ct); border: 1px solid color-mix(in srgb, var(--ct) 50%, transparent); border-radius: 7px; padding: 1px 7px; }
.cat-head h2 { font-size: 19px; direction: ltr; text-align: right; }
.cat-head .count { margin-inline-start: auto; font-size: 14px; color: var(--muted); }
.cat-block.is-empty { background: transparent; border-style: dashed; }
.cat-block.is-empty .cat-num { color: var(--muted); border-color: var(--rule-strong); }
.cat-block.is-empty .cat-head { padding: 10px 18px; }
.cat-block.is-empty .cat-head h2 { font-size: 16px; font-family: var(--font); font-weight: 600; color: var(--muted); }
.lesson-list { list-style: none; margin: 0; padding: 0 10px 10px; }
.lesson-row { display: flex; align-items: center; gap: 14px; padding: 12px; border-radius: 12px; background: var(--surface-2); border: 1px solid var(--rule); }
.lesson-row + .lesson-row { margin-top: 8px; }
.lesson-row .thumb { width: 120px; aspect-ratio: 16 / 9; border-radius: 8px; overflow: hidden; flex: none; border: 1px solid var(--rule); }
.lesson-row .thumb img { width: 100%; height: 100%; object-fit: cover; object-position: center top; }
.status { width: 28px; height: 28px; border-radius: 50%; display: grid; place-items: center; border: 2px solid var(--rule-strong); color: transparent; flex: none; cursor: pointer; background: transparent; transition: background-color .15s, border-color .15s; }
.status:hover { border-color: var(--ok); color: var(--ok); }
.status.done { background: var(--ok); border-color: var(--ok); color: var(--paper); }
.lesson-row .main { flex: 1; min-width: 0; }
.lesson-row .main a { font-weight: 700; font-size: 16.5px; }
.lesson-row .main a:hover { color: var(--ct); }
.lesson-row .main p { color: var(--muted); font-size: 14.5px; margin-top: 2px; }
.lesson-row .tags { display: flex; flex-wrap: wrap; gap: 6px; margin-top: 8px; }
@media (max-width: 600px) { .lesson-row { align-items: flex-start; flex-wrap: wrap; } .lesson-row .thumb { display: none; } }

/* ==========================================================================
   INNER PAGES
   ========================================================================== */
.page-head { padding: 40px 0 6px; }
.page-head h1 { font-size: clamp(30px, 4vw, 40px); }
.page-head p { color: var(--ink-2); margin-top: 10px; max-width: 64ch; }
.tabs { display: flex; gap: 4px; border-bottom: 1px solid var(--rule); margin: 26px 0 22px; overflow-x: auto; scrollbar-width: none; }
.tabs button { position: relative; display: inline-flex; align-items: center; gap: 8px; border: 0; background: none; padding: 12px; font-weight: 600; font-size: 15.5px; color: var(--muted); cursor: pointer; white-space: nowrap; }
.tabs button:hover { color: var(--ink); }
.tabs button[aria-selected="true"] { color: var(--ink); }
.tabs button[aria-selected="true"]::after { content: ""; position: absolute; inset: auto 8px -1px 8px; height: 2px; background: var(--signal); box-shadow: 0 0 10px var(--signal); }

.quiz-pick { grid-template-columns: repeat(auto-fill, minmax(250px, 1fr)); }
.quiz-pick .card { padding: 20px; text-align: start; cursor: pointer; border-top: 3px solid var(--ct); transition: transform .2s var(--ease), border-color .2s; }
.quiz-pick .card:hover { transform: translateY(-3px); border-color: var(--ct); }
.quiz-pick .card h3 { font-size: 22px; margin: 10px 0 4px; direction: ltr; text-align: right; }
.quiz-pick .best { margin-top: 10px; font-size: 14px; color: var(--muted); display: flex; gap: 6px; align-items: center; }
.quiz { max-width: 760px; margin: 0 auto; padding: 26px; }
.quiz-top { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-bottom: 14px; font-size: 14.5px; color: var(--muted); }
.quiz .progress { margin-bottom: 22px; }
.quiz h2 { font-family: var(--font); font-size: 20px; font-weight: 600; margin-bottom: 16px; line-height: 1.65; }
.quiz pre.code { margin-bottom: 16px; }
.options { display: grid; gap: 8px; }
.option { display: flex; align-items: center; gap: 12px; width: 100%; text-align: start; padding: 12px 14px; border-radius: 10px; border: 1.5px solid var(--rule-strong); background: var(--surface); cursor: pointer; font-size: 15.5px; transition: border-color .15s, background-color .15s; }
.option:hover:not([disabled]) { border-color: var(--signal); }
.option .key { width: 28px; height: 28px; border-radius: 7px; display: grid; place-items: center; background: var(--sunken); font-size: 13.5px; flex: none; font-weight: 700; border: 1px solid var(--rule); }
.option.correct { border-color: var(--ok); background: var(--ok-soft); }
.option.correct .key { background: var(--ok); color: var(--paper); border-color: var(--ok); }
.option.wrong { border-color: var(--bad); background: var(--bad-soft); }
.option.wrong .key { background: var(--bad); color: var(--paper); border-color: var(--bad); }
.option[disabled] { cursor: default; }
.explain { margin-top: 14px; padding: 14px 16px; border-radius: 10px; background: var(--sunken); border-inline-start: 3px solid var(--ok); font-size: 15px; }
.explain.bad { border-inline-start-color: var(--bad); }
.quiz-nav { display: flex; justify-content: space-between; gap: 10px; margin-top: 20px; }
.result { text-align: center; padding: 8px 0; }
.result .score { font-family: var(--mono); font-size: 60px; font-weight: 600; color: var(--signal); line-height: 1.2; direction: ltr; text-shadow: 0 0 24px rgba(34, 211, 238, .5); }
.result p { color: var(--muted); margin: 8px 0 20px; }
.review { text-align: start; margin-top: 24px; display: grid; gap: 10px; }
.review .item { padding: 14px 16px; border-radius: 10px; background: var(--sunken); font-size: 15px; }

.ch-grid { grid-template-columns: repeat(auto-fill, minmax(340px, 1fr)); align-items: start; }
@media (max-width: 400px) { .ch-grid { grid-template-columns: 1fr; } }
.ch { padding: 20px; display: flex; flex-direction: column; gap: 10px; }
.ch h3 { font-size: 19px; direction: ltr; text-align: right; }
.ch .row { display: flex; gap: 6px; flex-wrap: wrap; align-items: center; }
.ch .solved { margin-inline-start: auto; }
.ch details { border-top: 1px solid var(--rule); }
.ch summary { cursor: pointer; padding: 10px 0 6px; font-weight: 600; font-size: 15px; color: var(--ink-2); }
.lvl-1 { --c: #10b981; } .lvl-2 { --c: #f59e0b; } .lvl-3 { --c: #f43f5e; }

.lab-row { display: flex; align-items: center; gap: 14px; padding: 16px 18px; }
.lab-row:hover { border-color: var(--ct); }
.lab-row .ico { color: var(--ct); flex: none; }
.lab-row .t { font-weight: 600; }
.lab-row .s { font-size: 14px; color: var(--muted); }
.lab-row .go { display: none; }

.search-box { display: flex; align-items: center; gap: 10px; padding: 0 16px; background: var(--surface); border: 1.5px solid var(--rule-strong); border-radius: 12px; margin-top: 22px; max-width: 760px; color: var(--muted); }
.search-box:focus-within { border-color: var(--signal); box-shadow: 0 0 20px -6px rgba(34, 211, 238, .6); }
.search-box input { flex: 1; height: 54px; border: 0; outline: 0; background: transparent; color: var(--ink); font: inherit; font-size: 17px; min-width: 0; }
.result-item { display: block; padding: 16px 18px; }
.result-item:hover { border-color: var(--signal); }
.result-item .t { font-weight: 700; font-size: 16.5px; }
.result-item .p { font-size: 14px; color: var(--muted); display: flex; gap: 8px; align-items: center; flex-wrap: wrap; margin: 2px 0 6px; }
.result-item .snip { font-size: 15px; color: var(--ink-2); }
.index-status { font-size: 14px; color: var(--muted); margin: 12px 0; display: flex; align-items: center; gap: 8px; }
.spinner { width: 14px; height: 14px; border-radius: 50%; border: 2px solid var(--rule-strong); border-top-color: var(--signal); animation: spin .8s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }

.me-grid { grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); }
.cp { padding: 18px 20px; display: grid; gap: 10px; }
.cp:hover { border-color: var(--ct); }
.cp .top { display: flex; align-items: center; gap: 10px; }
.cp .top b { direction: ltr; font-family: var(--display); }
.cp .top span { margin-inline-start: auto; font-size: 14.5px; color: var(--muted); }
.data-tools { padding: 22px; display: grid; gap: 12px; }
.data-tools .row { display: flex; flex-wrap: wrap; gap: 10px; }

/* ==========================================================================
   LESSON VIEWER
   ========================================================================== */
body.page-lesson { height: 100vh; height: 100dvh; overflow: hidden; display: flex; flex-direction: column; background: var(--paper); }
.vbar { height: 48px; flex: none; display: flex; align-items: center; gap: 6px; padding: 0 10px; background: var(--paper); border-bottom: 1px solid var(--rule); z-index: 20; transition: margin-top .25s var(--ease); }
/* reading mode (page-lesson.js): the bar folds away while scrolling down, so the lesson gets the whole height */
body.bars-off .vbar { margin-top: -48px; }
@media (prefers-reduced-motion: reduce) { .vbar, .vfoot { transition: none; } }
.vbar .brand { display: inline-flex; align-items: center; gap: 8px; font-family: var(--display); font-weight: 700; direction: ltr; flex: none; }
.vbar .brand .logo { width: 28px; height: 28px; }
.vbar .brand span { font-size: 15px; }
.vbar .sep { width: 1px; height: 24px; background: var(--rule); margin: 0 6px; flex: none; }
.vtitle { min-width: 0; flex: 1; line-height: 1.35; }
.vtitle .crumb { font-size: 12.5px; color: var(--muted); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; display: block; }
.vtitle .crumb a:hover { color: var(--signal); }
.vtitle h1 { font-family: var(--font); font-size: 15.5px; font-weight: 700; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.vactions { display: flex; align-items: center; gap: 2px; }
.btn-done { min-height: 36px; padding: 0 12px; border-radius: 9px; border: 1.5px solid var(--rule-strong); background: transparent; color: var(--ink-2); font-weight: 600; font-size: 14px; display: inline-flex; align-items: center; gap: 6px; cursor: pointer; white-space: nowrap; }
.btn-done:hover { border-color: var(--ok); color: var(--ok); }
.btn-done[aria-pressed="true"] { background: var(--ok); border-color: var(--ok); color: var(--paper); }
.viewer { flex: 1; min-height: 0; display: grid; grid-template-columns: 300px 1fr; transition: grid-template-columns .25s var(--ease); }
.viewer.sb-closed { grid-template-columns: 0 1fr; }
.vside { min-width: 0; overflow: hidden; background: var(--surface); border-inline-end: 1px solid var(--rule); display: flex; flex-direction: column; }
.viewer.sb-closed .vside { border: 0; }
.vside-tabs { display: flex; gap: 2px; padding: 6px 10px 0; border-bottom: 1px solid var(--rule); flex: none; }
.vside-tabs button { flex: 1; border: 0; background: none; padding: 10px 4px; font-weight: 600; font-size: 14px; color: var(--muted); cursor: pointer; position: relative; white-space: nowrap; }
.vside-tabs button[aria-selected="true"] { color: var(--ink); }
.vside-tabs button[aria-selected="true"]::after { content: ""; position: absolute; inset: auto 8px -1px; height: 2px; background: var(--signal); }
.vside-body { flex: 1; overflow-y: auto; padding: 8px 10px 16px; overscroll-behavior: contain; }
.vside-prog { padding: 12px 14px; border-bottom: 1px solid var(--rule); font-size: 13.5px; color: var(--muted); display: grid; gap: 6px; flex: none; }
.vside-prog div:first-child { display: flex; justify-content: space-between; }
.side-cat { font-size: 13px; font-weight: 700; color: var(--muted); padding: 12px 8px 4px; direction: ltr; text-align: right; display: flex; gap: 6px; justify-content: flex-end; }
.side-cat.empty { font-weight: 400; opacity: .75; }
.side-lesson { display: flex; align-items: center; gap: 10px; padding: 8px; border-radius: 8px; font-size: 14.5px; color: var(--ink-2); }
.side-lesson:hover { background: var(--surface-2); }
.side-lesson[aria-current="page"] { background: var(--surface-2); color: var(--ink); font-weight: 700; box-shadow: inset -3px 0 0 var(--ct); }
.side-lesson .st { width: 18px; height: 18px; border-radius: 50%; border: 2px solid var(--rule-strong); display: grid; place-items: center; flex: none; color: transparent; }
.side-lesson .st.done { background: var(--ok); border-color: var(--ok); color: var(--paper); }
.outline a { display: block; padding: 6px 10px; border-radius: 7px; font-size: 14px; color: var(--ink-2); border-inline-start: 2px solid transparent; }
.outline a:hover { background: var(--surface-2); }
.outline a.active { color: var(--ink); font-weight: 600; border-inline-start-color: var(--signal); background: var(--surface-2); }
.outline a.lvl-3 { padding-inline-start: 22px; font-size: 13.5px; }
.vmain { position: relative; min-width: 0; min-height: 0; display: flex; flex-direction: column; background: var(--paper); }
.vframe { flex: 1; width: 100%; border: 0; background: #fff; display: block; }
.vloading { position: absolute; inset: 0; display: grid; place-items: center; background: var(--paper); z-index: 2; transition: opacity .25s; }
.vloading.gone { opacity: 0; pointer-events: none; }
.vloading .box { text-align: center; color: var(--muted); }
.vloading .spinner { width: 28px; height: 28px; border-width: 3px; margin: 0 auto 12px; }
.verror { position: absolute; inset: 0; display: grid; place-items: center; padding: 24px; background: var(--paper); z-index: 3; }
.vfoot { flex: none; display: flex; align-items: center; justify-content: space-between; gap: 10px; padding: 0 12px; background: var(--paper); border-top: 0 solid var(--rule); max-height: 0; overflow: hidden; transition: max-height .25s var(--ease), padding .25s var(--ease); }
/* hidden while reading; slides in near the end of the lesson (page-lesson.js) */
.vfoot.show { max-height: 84px; padding: 6px 12px; border-top-width: 1px; }
.vfoot a { display: flex; align-items: center; gap: 10px; min-width: 0; max-width: 46%; padding: 6px 10px; border-radius: 8px; }
.vfoot a:hover { background: var(--surface-2); }
.vfoot a .l { font-size: 12.5px; color: var(--muted); display: block; }
.vfoot a .t { font-size: 14.5px; font-weight: 600; display: block; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.vfoot a.next { margin-inline-start: auto; text-align: end; }
.vfoot .ph { color: var(--muted); font-size: 13.5px; padding: 6px 10px; }
.fs-exit { position: absolute; top: 12px; inset-inline-start: 12px; z-index: 5; display: none; background: var(--surface); }
.vmain:fullscreen .fs-exit, body.focus .fs-exit { display: inline-flex; }
.vmain:fullscreen .vfoot { display: none; }
body.focus .vbar, body.focus .vside, body.focus .vfoot { display: none; }
body.focus .viewer { grid-template-columns: 0 1fr; }
.side-scrim { display: none; }
@media (max-width: 900px) {
  .viewer, .viewer.sb-closed { grid-template-columns: 1fr; }
  .vside { position: fixed; z-index: 40; top: 48px; bottom: 0; inset-inline-start: 0; width: min(340px, 88vw); transform: translateX(100%); transition: transform .25s var(--ease); border: 0; box-shadow: 0 0 40px rgba(0, 0, 0, .5); }
  .viewer.sb-open .vside { transform: none; }
  .viewer.sb-open .side-scrim { display: block; position: fixed; inset: 48px 0 0 0; z-index: 35; background: rgba(3, 7, 18, .55); }
  .vbar .brand span, .vbar .sep.hide-sm { display: none; }
  .hide-sm { display: none !important; }
  .btn-done .lbl { display: none; }
}
@media (max-width: 520px) { .vbar { gap: 2px; padding: 0 6px; } .vbar .icon-btn { width: 36px; height: 36px; } .hide-xs { display: none !important; } }

.notfound { text-align: center; padding: 96px 0 40px; }
.notfound .code { font-family: var(--mono); font-size: 96px; font-weight: 600; color: var(--signal); line-height: 1; text-shadow: 0 0 30px rgba(34, 211, 238, .5); }
.punchcard { direction: ltr; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: .01ms !important; animation-iteration-count: 1 !important; transition-duration: .01ms !important; }
}
@media print { .rail, .topbar, .site-footer, .toasts { display: none; } body.has-rail { padding: 0; } }