/* GPU Kernel Optimization course — styles */
:root {
  --bg: #0d1117;
  --bg-alt: #11161d;
  --panel: #161b22;
  --panel-2: #1b212a;
  --border: #283039;
  --border-soft: #21272f;
  --text: #d7dde3;
  --text-dim: #9aa4af;
  --text-faint: #6b7682;
  --accent: #58c7f3;
  --accent-2: #7ee787;
  --accent-warm: #ffb454;
  --purple: #bc8cff;
  --pink: #ff7b9c;
  --green: #3fb950;
  --red: #f85149;
  --radius: 10px;
  --mono: "SFMono-Regular", "JetBrains Mono", "Fira Code", Consolas, "Liberation Mono", monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: var(--sans);
  background: var(--bg);
  color: var(--text);
  font-size: 16px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* layout ---------------------------------------------------------------- */
.shell { display: flex; min-height: 100vh; }

.sidebar {
  width: 304px; flex: 0 0 304px;
  background: var(--bg-alt);
  border-right: 1px solid var(--border);
  display: flex; flex-direction: column;
  height: 100vh; position: sticky; top: 0;
}
.brand {
  padding: 18px 20px 14px; border-bottom: 1px solid var(--border);
}
.brand a { color: var(--text); text-decoration: none; display: block; }
.brand-title { font-weight: 700; font-size: 15px; letter-spacing: .2px; }
.brand-sub { font-size: 12px; color: var(--text-faint); margin-top: 2px; }
.brand-mark {
  display: inline-block; width: 22px; height: 22px; border-radius: 6px; margin-right: 8px;
  background: linear-gradient(135deg, var(--accent), var(--purple));
  vertical-align: -5px; position: relative;
}
.brand-mark::after {
  content: ""; position: absolute; inset: 5px; border-radius: 3px;
  background: repeating-linear-gradient(90deg, rgba(13,17,23,.9) 0 2px, transparent 2px 4px);
}

.progress-wrap { padding: 12px 20px; border-bottom: 1px solid var(--border); }
.progress-label { font-size: 11px; color: var(--text-faint); margin-bottom: 6px; }
.progress-track { height: 5px; background: var(--panel-2); border-radius: 4px; overflow: hidden; }
.progress-fill {
  height: 100%; width: 0%;
  background: linear-gradient(90deg, var(--accent), var(--accent-2));
  transition: width .4s ease;
}

.nav { overflow-y: auto; padding: 8px 0 40px; flex: 1; }
.nav-part { padding: 6px 0; }
.nav-part-title {
  font-size: 11px; text-transform: uppercase; letter-spacing: .08em;
  color: var(--text-faint); padding: 12px 20px 6px; font-weight: 700;
}
.nav-link {
  display: flex; align-items: center; gap: 9px;
  padding: 6px 20px 6px 18px; color: var(--text-dim); font-size: 13.5px;
  border-left: 2px solid transparent;
}
.nav-link:hover { background: var(--panel); color: var(--text); text-decoration: none; }
.nav-link.active {
  color: var(--text); background: var(--panel);
  border-left-color: var(--accent); font-weight: 600;
}
.nav-text { line-height: 1.35; }
.nav-dot {
  width: 8px; height: 8px; border-radius: 50%; flex: 0 0 8px;
  border: 1.5px solid var(--border); background: transparent;
}
.nav-dot.done { background: var(--accent-2); border-color: var(--accent-2); }

/* content --------------------------------------------------------------- */
.content { flex: 1; min-width: 0; height: 100vh; overflow-y: auto; }
.topbar {
  display: none; align-items: center; gap: 12px;
  padding: 12px 16px; border-bottom: 1px solid var(--border);
  position: sticky; top: 0; background: var(--bg); z-index: 20;
}
#nav-toggle {
  background: var(--panel); border: 1px solid var(--border); color: var(--text);
  border-radius: 8px; padding: 6px 10px; cursor: pointer; font-size: 18px;
}
.main { padding: 0; }

.article {
  max-width: 860px; margin: 0 auto; padding: 44px 40px 90px;
}
.article-kicker {
  font-size: 12px; text-transform: uppercase; letter-spacing: .1em;
  color: var(--accent); font-weight: 700; margin-bottom: 8px;
}
.article h1 {
  font-size: 33px; line-height: 1.2; margin: 6px 0 18px; letter-spacing: -.01em;
}
.article h2 {
  font-size: 23px; margin: 38px 0 12px; padding-top: 10px;
  border-top: 1px solid var(--border-soft); letter-spacing: -.01em;
}
.article h3 { font-size: 18px; margin: 26px 0 8px; }
.article p { margin: 12px 0; }
.article ul, .article ol { margin: 12px 0; padding-left: 24px; }
.article li { margin: 5px 0; }
.article strong { color: #fff; }
.article hr { border: none; border-top: 1px solid var(--border); margin: 30px 0; }
.article img { max-width: 100%; border-radius: var(--radius); }
.article table { border-collapse: collapse; margin: 16px 0; width: 100%; font-size: 14px; display: block; overflow-x: auto; }
.article th, .article td { border: 1px solid var(--border); padding: 7px 11px; text-align: left; }
.article th { background: var(--panel); }
.article blockquote {
  margin: 16px 0; padding: 2px 16px; border-left: 3px solid var(--border);
  color: var(--text-dim);
}

/* inline code + code blocks --------------------------------------------- */
code {
  font-family: var(--mono); font-size: .88em;
  background: var(--panel-2); padding: .12em .4em; border-radius: 5px;
  color: #e6c07b;
}
.codeblock { position: relative; margin: 16px 0; }
.codeblock .code-lang {
  position: absolute; top: 0; right: 0;
  font-family: var(--mono); font-size: 10px; text-transform: uppercase;
  letter-spacing: .08em; color: var(--text-faint);
  background: var(--panel); border: 1px solid var(--border);
  border-top: none; border-right: none;
  padding: 2px 8px; border-bottom-left-radius: 8px; border-top-right-radius: var(--radius);
}
.codeblock pre {
  margin: 0; background: var(--panel); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 14px 16px; overflow-x: auto;
  font-family: var(--mono); font-size: 13px; line-height: 1.55;
}
.codeblock pre code { background: none; padding: 0; color: var(--text); font-size: 13px; }

/* callouts -------------------------------------------------------------- */
.callout {
  margin: 18px 0; border-radius: var(--radius); padding: 12px 16px 4px;
  border: 1px solid var(--border); background: var(--panel);
  border-left-width: 3px;
}
.callout-title { font-weight: 700; font-size: 13px; margin-bottom: 2px; }
.callout-body p { margin: 6px 0 10px; }
.callout-note { border-left-color: var(--accent); }
.callout-note .callout-title { color: var(--accent); }
.callout-tip, .callout-key { border-left-color: var(--accent-2); }
.callout-tip .callout-title, .callout-key .callout-title { color: var(--accent-2); }
.callout-warning { border-left-color: var(--accent-warm); }
.callout-warning .callout-title { color: var(--accent-warm); }
.callout-important { border-left-color: var(--pink); }
.callout-important .callout-title { color: var(--pink); }
.callout-gpu { border-left-color: var(--purple); }
.callout-gpu .callout-title { color: var(--purple); }
.callout-site { border-left-color: var(--accent-warm); background: linear-gradient(90deg, rgba(255,180,84,.06), var(--panel) 40%); }
.callout-site .callout-title { color: var(--accent-warm); }
.callout-field { border-left-color: var(--pink); }
.callout-field .callout-title { color: var(--pink); }
.callout-numbers { border-left-color: var(--purple); }
.callout-numbers .callout-title { color: var(--purple); }
.home-footer { margin-top: 34px; padding-top: 18px; border-top: 1px solid var(--border-soft); color: var(--text-dim); font-size: 14px; }

/* playground ------------------------------------------------------------ */
.pg {
  margin: 22px 0; border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--panel); overflow: hidden;
}
.pg-head {
  display: flex; align-items: center; justify-content: space-between; gap: 10px;
  padding: 10px 14px; background: var(--panel-2); border-bottom: 1px solid var(--border);
}
.pg-title { font-weight: 700; font-size: 14px; }
.pg-badge {
  font-size: 10.5px; text-transform: uppercase; letter-spacing: .06em;
  padding: 3px 8px; border-radius: 20px; font-weight: 700;
}
.pg-badge.wgsl { background: rgba(88,199,243,.12); color: var(--accent); }
.pg-badge.cuda { background: rgba(126,231,135,.12); color: var(--accent-2); }
.pg-prelude {
  display: flex; align-items: center; gap: 10px;
  padding: 8px 14px; background: rgba(188,140,255,.06);
  border-bottom: 1px solid var(--border-soft);
  font-family: var(--mono); font-size: 12px; color: var(--text-dim);
  overflow-x: auto;
}
.pg-prelude code { background: none; color: var(--purple); padding: 0; white-space: pre; }
.pg-prelude-tag {
  font-family: var(--sans); font-size: 9.5px; text-transform: uppercase;
  letter-spacing: .08em; color: var(--purple); border: 1px solid rgba(188,140,255,.3);
  border-radius: 4px; padding: 1px 5px; flex: 0 0 auto;
}
.pg-contract {
  padding: 7px 14px; font-size: 11.5px; color: var(--text-faint);
  line-height: 1.55; border-bottom: 1px solid var(--border-soft);
}
.pg-note { padding: 8px 14px; font-size: 13.5px; color: var(--text-dim); border-bottom: 1px solid var(--border-soft); }
.pg-note code { font-size: 12px; }
.pg .CodeMirror {
  height: auto; font-family: var(--mono); font-size: 13px; line-height: 1.5;
  background: var(--panel);
}
.pg-bar {
  display: flex; align-items: center; gap: 10px;
  padding: 10px 14px; border-top: 1px solid var(--border); flex-wrap: wrap;
}
.pg-btn {
  font-family: var(--sans); font-size: 13px; font-weight: 600;
  border-radius: 8px; padding: 7px 14px; cursor: pointer; border: 1px solid transparent;
}
.pg-run { background: var(--accent); color: #05222e; }
.pg-run:hover { background: #7ad2f5; }
.pg-run:disabled { opacity: .5; cursor: default; }
.pg-ghost { background: transparent; border-color: var(--border); color: var(--text-dim); }
.pg-ghost:hover { color: var(--text); border-color: var(--text-faint); }
.pg-status { font-size: 12.5px; color: var(--text-faint); margin-left: auto; }
.pg-status.running { color: var(--accent); }
.pg-status.ok { color: var(--green); }
.pg-status.fail { color: var(--red); }

.pg-out { padding: 0 14px 14px; }
.pg-verdict {
  display: flex; gap: 12px; align-items: flex-start;
  padding: 12px 14px; border-radius: 8px; margin-top: 4px;
}
.pg-verdict.ok { background: rgba(63,185,80,.1); border: 1px solid rgba(63,185,80,.3); }
.pg-verdict.bad { background: rgba(248,81,73,.08); border: 1px solid rgba(248,81,73,.3); }
.pg-verdict-icon { font-size: 20px; line-height: 1.2; }
.pg-verdict.ok .pg-verdict-icon { color: var(--green); }
.pg-verdict.bad .pg-verdict-icon { color: var(--red); }
.pg-verdict-sum { font-weight: 600; }
.pg-verdict-det { font-size: 12.5px; color: var(--text-dim); font-family: var(--mono); margin-top: 3px; }

.pg-metrics { display: flex; gap: 10px; margin-top: 12px; flex-wrap: wrap; }
.pg-metric {
  flex: 1; min-width: 120px; background: var(--panel-2);
  border: 1px solid var(--border); border-radius: 8px; padding: 10px 12px;
}
.pg-metric-val { font-family: var(--mono); font-size: 18px; font-weight: 700; color: var(--accent); }
.pg-metric-lab { font-size: 11px; color: var(--text-faint); text-transform: uppercase; letter-spacing: .05em; margin-top: 2px; }

.pg-compare { margin-top: 10px; font-size: 13px; color: var(--text-dim); padding: 8px 12px; border-radius: 8px; background: var(--panel-2); }
.pg-compare.good { color: var(--accent-2); }

.pg-error { margin-top: 8px; }
.pg-error-title { color: var(--red); font-weight: 700; font-size: 13px; margin-bottom: 4px; }
.pg-error pre {
  margin: 0; background: rgba(248,81,73,.06); border: 1px solid rgba(248,81,73,.25);
  border-radius: 8px; padding: 10px 12px; font-family: var(--mono); font-size: 12px;
  white-space: pre-wrap; color: #ffb3ae; overflow-x: auto;
}

/* home ------------------------------------------------------------------ */
.hero { padding: 18px 0 30px; }
.hero-kicker { color: var(--accent); font-weight: 700; text-transform: uppercase; letter-spacing: .1em; font-size: 12px; }
.hero h1 { font-size: 40px; line-height: 1.12; margin: 10px 0 16px; letter-spacing: -.02em; }
.hero-sub { font-size: 17px; color: var(--text-dim); max-width: 640px; }
.hero-actions { display: flex; gap: 12px; margin: 24px 0 0; flex-wrap: wrap; }
.btn-primary, .btn-secondary {
  display: inline-block; padding: 11px 20px; border-radius: 9px; font-weight: 700; font-size: 14px;
}
.btn-primary { background: var(--accent); color: #05222e; }
.btn-primary:hover { background: #7ad2f5; text-decoration: none; }
.btn-secondary { border: 1px solid var(--border); color: var(--text); }
.btn-secondary:hover { border-color: var(--text-faint); text-decoration: none; }
.hero-stats { display: flex; gap: 34px; margin-top: 34px; }
.hero-stats > div { display: flex; flex-direction: column; font-size: 12px; color: var(--text-faint); text-transform: uppercase; letter-spacing: .05em; }
.hero-stats span { font-size: 26px; font-weight: 700; color: var(--text); font-family: var(--mono); }
.home-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 18px 30px; margin-top: 26px; }
.home-part h3 { font-size: 15px; margin: 0 0 6px; padding-bottom: 6px; border-bottom: 1px solid var(--border-soft); }
.home-part ul { list-style: none; padding: 0; margin: 0; }
.home-part li { font-size: 13.5px; margin: 4px 0; color: var(--text-dim); }
.mini-done { color: var(--accent-2); font-size: 11px; }

/* setup ----------------------------------------------------------------- */
.gpu-table { font-family: var(--mono); font-size: 13px; }
.gpu-table td:first-child { color: var(--text-dim); width: 280px; }

/* footer nav ------------------------------------------------------------ */
.lesson-foot { display: flex; justify-content: space-between; gap: 16px; margin-top: 48px; padding-top: 22px; border-top: 1px solid var(--border); }
.foot-link { display: flex; flex-direction: column; padding: 12px 16px; border: 1px solid var(--border); border-radius: var(--radius); max-width: 48%; }
.foot-link:hover { border-color: var(--accent); text-decoration: none; }
.foot-link.next { text-align: right; margin-left: auto; }
.foot-dir { font-size: 12px; color: var(--text-faint); }
.foot-name { font-weight: 600; color: var(--text); margin-top: 2px; }

.loading { padding: 60px; text-align: center; color: var(--text-faint); }

/* CodeMirror theme (shared by editor + highlighted code blocks) --------- */
.CodeMirror { color: var(--text); }
.cm-s-default .cm-keyword, .CodeMirror .cm-keyword { color: var(--pink); }
.cm-s-default .cm-atom, .CodeMirror .cm-atom { color: var(--accent-warm); }
.cm-s-default .cm-number, .CodeMirror .cm-number { color: var(--accent-2); }
.cm-s-default .cm-def, .CodeMirror .cm-def { color: var(--accent); }
.cm-s-default .cm-variable, .CodeMirror .cm-variable { color: var(--text); }
.cm-s-default .cm-variable-2, .CodeMirror .cm-variable-2 { color: #79c0ff; }
.cm-s-default .cm-variable-3, .CodeMirror .cm-variable-3, .cm-s-default .cm-type { color: var(--purple); }
.cm-s-default .cm-property, .CodeMirror .cm-property { color: #79c0ff; }
.cm-s-default .cm-comment, .CodeMirror .cm-comment { color: var(--text-faint); font-style: italic; }
.cm-s-default .cm-string, .CodeMirror .cm-string { color: #a5d6ff; }
.cm-s-default .cm-string-2, .CodeMirror .cm-string-2 { color: #a5d6ff; }
.cm-s-default .cm-meta, .CodeMirror .cm-meta { color: var(--purple); }
.cm-s-default .cm-builtin, .CodeMirror .cm-builtin { color: var(--accent); }
.cm-s-default .cm-operator, .CodeMirror .cm-operator { color: var(--pink); }
.cm-s-default .cm-bracket, .CodeMirror .cm-bracket { color: var(--text-dim); }
.CodeMirror-cursor { border-left: 1px solid var(--text) !important; }
.CodeMirror-selected { background: rgba(88,199,243,.18) !important; }
.cm-s-default div.CodeMirror-selected { background: rgba(88,199,243,.18); }
.CodeMirror-gutters { background: var(--panel-2); border-right: 1px solid var(--border); }
.CodeMirror-linenumber { color: var(--text-faint); }
.CodeMirror-activeline-background { background: rgba(255,255,255,.025); }
.CodeMirror-matchingbracket { color: var(--accent-2) !important; font-weight: 700; }

/* responsive ------------------------------------------------------------ */
@media (max-width: 900px) {
  .sidebar {
    position: fixed; left: 0; top: 0; z-index: 40; transform: translateX(-100%);
    transition: transform .25s ease; box-shadow: 0 0 40px rgba(0,0,0,.5);
  }
  body.nav-open .sidebar { transform: translateX(0); }
  .topbar { display: flex; }
  .article { padding: 26px 18px 70px; }
  .home-grid { grid-template-columns: 1fr; }
  .hero h1 { font-size: 30px; }
  .foot-link { max-width: 49%; }
}

/* figures (inline SVG teaching diagrams, see assets/js/figures.js) -------- */
.fig { margin: 28px 0 32px; }
.fig-frame {
  background: var(--bg-alt); border: 1px solid var(--border-soft);
  border-radius: var(--radius); padding: 18px 14px 12px;
}
.fig svg { width: 100%; height: auto; display: block; font-family: var(--sans); }
.fig figcaption {
  margin-top: 10px; font-size: 12.5px; color: var(--text-faint);
  text-align: center; line-height: 1.55; padding: 0 18px;
}
.fig svg text { font-family: var(--sans); }
.fg-t { fill: var(--text); font-size: 12px; }
.fg-d { fill: var(--text-dim); font-size: 11px; }
.fg-f { fill: var(--text-faint); font-size: 10px; }
.fg-m { font-family: var(--mono); }
.fg-b { font-weight: 700; }

/* AI tutor (right-side chat panel, see assets/js/tutor.js) ---------------- */
.tutor-fab {
  position: fixed; right: 22px; bottom: 22px; z-index: 60;
  width: 52px; height: 52px; border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--purple));
  color: #0d1117; font-size: 22px; border: none; cursor: pointer;
  box-shadow: 0 4px 24px rgba(88,199,243,.35);
  transition: transform .15s ease;
}
.tutor-fab:hover { transform: scale(1.06); }
.tutor-fab.open { right: 442px; }
.tutor-panel {
  position: fixed; top: 0; right: 0; bottom: 0; z-index: 55;
  width: 420px; max-width: 96vw;
  background: var(--bg-alt); border-left: 1px solid var(--border);
  box-shadow: -12px 0 40px rgba(0,0,0,.45);
  display: flex; flex-direction: column;
  transform: translateX(105%); transition: transform .22s ease;
}
.tutor-panel.open { transform: translateX(0); }
.tutor-head {
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px 14px; border-bottom: 1px solid var(--border);
}
.tutor-title { font-weight: 700; font-size: 14px; }
.tutor-powered { color: var(--text-faint); font-weight: 400; font-size: 11.5px; }
.tutor-head-btns { display: flex; gap: 6px; }
.tutor-mini-btn {
  background: var(--panel); color: var(--text-dim); border: 1px solid var(--border);
  border-radius: 6px; font-size: 11px; padding: 3px 8px; cursor: pointer;
}
.tutor-mini-btn:hover { color: var(--text); border-color: var(--accent); }
.tutor-ctx {
  padding: 6px 14px; font-size: 11px; color: var(--text-faint);
  border-bottom: 1px solid var(--border-soft);
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.tutor-settings {
  display: none; padding: 12px 14px; border-bottom: 1px solid var(--border);
  background: var(--panel);
}
.tutor-settings label { display: block; font-size: 11px; color: var(--text-faint); margin: 8px 0 4px; }
.tutor-settings input, .tutor-settings select {
  width: 100%; background: var(--bg); color: var(--text);
  border: 1px solid var(--border); border-radius: 6px; padding: 7px 9px;
  font-size: 12.5px; font-family: var(--mono);
}
.tutor-settings select { font-family: var(--sans); }
.tutor-settings-note { font-size: 10.5px; color: var(--text-faint); margin: 8px 0; }
.tutor-settings .tutor-save { margin-top: 2px; }
.tutor-log { flex: 1; overflow-y: auto; padding: 14px; }
.tutor-msg { margin-bottom: 14px; display: flex; }
.tutor-msg.user { justify-content: flex-end; }
.tutor-msg-body {
  max-width: 92%; font-size: 13.5px; line-height: 1.55; color: var(--text);
  overflow-wrap: break-word;
}
.tutor-msg.user .tutor-msg-body {
  background: rgba(88,199,243,.12); border: 1px solid rgba(88,199,243,.25);
  border-radius: 12px 12px 3px 12px; padding: 8px 12px; white-space: pre-wrap;
}
.tutor-msg.assistant .tutor-msg-body { width: 100%; }
.tutor-prose p { margin: 0 0 10px; }
.tutor-prose p:last-child { margin-bottom: 0; }
.tutor-prose ul, .tutor-prose ol { margin: 0 0 10px; padding-left: 20px; }
.tutor-prose li { margin-bottom: 3px; }
.tutor-prose code {
  background: var(--panel-2); border-radius: 4px; padding: 1px 5px;
  font-family: var(--mono); font-size: 12px;
}
.tutor-prose strong { color: var(--accent-2); }
.tutor-prose h1, .tutor-prose h2, .tutor-prose h3 { font-size: 14px; margin: 12px 0 6px; }
.tutor-code {
  background: var(--panel); border: 1px solid var(--border-soft); border-radius: 8px;
  padding: 10px 12px; margin: 8px 0; overflow-x: auto;
  font-family: var(--mono); font-size: 12px; line-height: 1.5; color: var(--text-dim);
}
.tutor-drawing { margin: 10px 0; }
.tutor-drawing iframe {
  width: 100%; height: 320px; border: 1px solid var(--border);
  border-radius: var(--radius); background: var(--bg);
}
.tutor-drawing-bar { margin-top: 4px; text-align: right; }
.tutor-drawing-pending {
  margin: 10px 0; padding: 14px; text-align: center; font-size: 12px;
  color: var(--text-faint); border: 1px dashed var(--border); border-radius: var(--radius);
}
.tutor-cursor { color: var(--accent); animation: tutor-blink 1s step-start infinite; }
@keyframes tutor-blink { 50% { opacity: 0; } }
.tutor-error {
  color: var(--red); font-size: 12.5px; background: rgba(248,81,73,.08);
  border: 1px solid rgba(248,81,73,.3); border-radius: 8px; padding: 8px 12px;
}
.tutor-suggest { padding: 0 14px 8px; display: flex; flex-wrap: wrap; gap: 6px; }
.tutor-chip {
  background: var(--panel); color: var(--text-dim); border: 1px solid var(--border);
  border-radius: 14px; font-size: 11.5px; padding: 5px 11px; cursor: pointer;
}
.tutor-chip:hover { color: var(--text); border-color: var(--accent); }
.tutor-inputrow {
  display: flex; gap: 8px; align-items: flex-end;
  padding: 10px 14px 14px; border-top: 1px solid var(--border);
}
.tutor-input {
  flex: 1; resize: none; background: var(--panel); color: var(--text);
  border: 1px solid var(--border); border-radius: 10px; padding: 9px 12px;
  font-size: 13px; font-family: var(--sans); line-height: 1.4; max-height: 120px;
}
.tutor-input:focus { outline: none; border-color: var(--accent); }
.tutor-send {
  background: var(--accent); color: #0d1117; border: none; border-radius: 10px;
  width: 38px; height: 38px; font-size: 15px; cursor: pointer; flex: 0 0 auto;
}
.tutor-send:disabled { opacity: .4; cursor: default; }
@media (max-width: 900px) {
  .tutor-panel { width: 100vw; max-width: 100vw; }
  .tutor-fab.open { display: none; }
}

/* sibling-course brand mark (datacenter/) */
.brand-mark.dc { background: linear-gradient(135deg, var(--accent-warm), var(--pink)); }