/* ---------------------------------------------------------------
   Design tokens
   --------------------------------------------------------------- */
:root {
  --bg: #ffffff;
  --bg-raised: #f5f7fa;
  --bg-sunken: #eef1f6;
  --text: #1b2430;
  --text-dim: #56606f;
  --border: #dde3ec;

  --accent: #007d9c;
  --accent-strong: #005f78;
  --accent-bg: #e3f4f8;

  --ok: #1a7f4e;
  --ok-bg: #e5f6ec;
  --warn: #a35a00;
  --warn-bg: #fdf1de;
  --danger: #b3261e;
  --danger-bg: #fce8e6;

  --code-bg: #0f1720;
  --code-text: #e6edf3;
  --code-border: #253143;

  --shadow: 0 1px 2px rgba(16, 24, 40, 0.06), 0 1px 3px rgba(16, 24, 40, 0.08);
  --shadow-lg: 0 4px 12px rgba(16, 24, 40, 0.12), 0 2px 4px rgba(16, 24, 40, 0.08);

  --radius-sm: 6px;
  --radius: 10px;
  --radius-lg: 16px;

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Consolas, "Liberation Mono", Menlo, monospace;

  --maxw: 780px;
  --gopher-cyan: #00acd7;
}

:root[data-theme="dark"] {
  --bg: #0d1117;
  --bg-raised: #151b23;
  --bg-sunken: #010409;
  --text: #e6edf3;
  --text-dim: #9aa7b7;
  --border: #2a323d;

  --accent: #4fd1e8;
  --accent-strong: #7fe0f0;
  --accent-bg: #10313a;

  --ok: #56d394;
  --ok-bg: #0f2d21;
  --warn: #f0b354;
  --warn-bg: #34260c;
  --danger: #f38b83;
  --danger-bg: #3a1614;

  --code-bg: #0a0e14;
  --code-text: #e6edf3;
  --code-border: #1f2733;

  --shadow: 0 1px 2px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.45);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0d1117;
    --bg-raised: #151b23;
    --bg-sunken: #010409;
    --text: #e6edf3;
    --text-dim: #9aa7b7;
    --border: #2a323d;

    --accent: #4fd1e8;
    --accent-strong: #7fe0f0;
    --accent-bg: #10313a;

    --ok: #56d394;
    --ok-bg: #0f2d21;
    --warn: #f0b354;
    --warn-bg: #34260c;
    --danger: #f38b83;
    --danger-bg: #3a1614;

    --code-bg: #0a0e14;
    --code-text: #e6edf3;
    --code-border: #1f2733;

    --shadow: 0 1px 2px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 24px rgba(0, 0, 0, 0.45);
  }
}

/* ---------------------------------------------------------------
   Reset + base
   --------------------------------------------------------------- */
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.65;
  transition: background-color 0.15s ease, color 0.15s ease;
}
h1, h2, h3, h4 { line-height: 1.25; font-weight: 700; letter-spacing: -0.01em; }
h1 { font-size: 2.1rem; margin: 0 0 0.4em; }
h2 { font-size: 1.5rem; margin: 2.2em 0 0.6em; }
h3 { font-size: 1.15rem; margin: 1.6em 0 0.5em; }
p { margin: 0 0 1.1em; color: var(--text); }
a { color: var(--accent-strong); text-decoration-color: color-mix(in srgb, var(--accent-strong) 40%, transparent); }
:root[data-theme="dark"] a, @media (prefers-color-scheme: dark) { }
a:hover { text-decoration-thickness: 2px; }
img, svg { max-width: 100%; }
code { font-family: var(--font-mono); font-size: 0.9em; }
:not(pre) > code {
  background: var(--bg-sunken);
  padding: 0.15em 0.4em;
  border-radius: 4px;
  border: 1px solid var(--border);
}

/* ---------------------------------------------------------------
   Layout
   --------------------------------------------------------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.9rem 1.5rem;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}
.brand {
  display: flex;
  align-items: center;
  gap: 0.55rem;
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--text);
  text-decoration: none;
}
.brand .dot {
  width: 11px; height: 11px; border-radius: 50%;
  background: var(--gopher-cyan);
  box-shadow: 0 0 0 3px var(--accent-bg);
}
.nav-links { display: flex; align-items: center; gap: 1.25rem; font-size: 0.92rem; }
.nav-links a { color: var(--text-dim); text-decoration: none; font-weight: 600; }
.nav-links a:hover, .nav-links a.active { color: var(--accent-strong); }

.theme-toggle {
  border: 1px solid var(--border);
  background: var(--bg-raised);
  color: var(--text);
  border-radius: var(--radius-sm);
  padding: 0.45em 0.85em;
  display: inline-flex; align-items: center; justify-content: center;
  cursor: pointer;
  font-size: 0.82rem;
  font-weight: 600;
  white-space: nowrap;
}
.theme-toggle:hover { border-color: var(--accent); }

main { display: block; }
.page {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 2.5rem 1.5rem 6rem;
}
.page-wide {
  max-width: 980px;
  margin: 0 auto;
  padding: 2.5rem 1.5rem 6rem;
}
.eyebrow {
  display: inline-block;
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--accent-strong);
  background: var(--accent-bg);
  padding: 0.25em 0.7em;
  border-radius: 999px;
  margin-bottom: 0.9rem;
}
.lede { font-size: 1.15rem; color: var(--text-dim); }

footer.site-footer {
  text-align: center;
  color: var(--text-dim);
  font-size: 0.85rem;
  padding: 2rem 1.5rem 3rem;
  border-top: 1px solid var(--border);
  margin-top: 3rem;
}

/* ---------------------------------------------------------------
   Buttons
   --------------------------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.45em;
  font-family: var(--font-sans);
  font-size: 0.92rem;
  font-weight: 600;
  padding: 0.5em 1em;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg-raised);
  color: var(--text);
  cursor: pointer;
  transition: transform 0.08s ease, border-color 0.15s ease, background 0.15s ease;
  text-decoration: none;
}
.btn:hover { border-color: var(--accent); }
.btn:active { transform: translateY(1px); }
.btn-primary {
  background: var(--gopher-cyan);
  border-color: var(--gopher-cyan);
  color: #04262d;
}
.btn-primary:hover { filter: brightness(1.05); }
.btn-primary:disabled, .btn:disabled {
  opacity: 0.5; cursor: not-allowed; filter: none;
}
.btn-sm { font-size: 0.82rem; padding: 0.35em 0.75em; }

/* ---------------------------------------------------------------
   Code blocks + Run button
   --------------------------------------------------------------- */
.code-panel {
  background: var(--code-bg);
  color: var(--code-text);
  border: 1px solid var(--code-border);
  border-radius: var(--radius);
  margin: 1.4rem 0;
  overflow: hidden;
  box-shadow: var(--shadow);
}
.code-panel-head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.55rem 0.9rem;
  border-bottom: 1px solid var(--code-border);
  background: color-mix(in srgb, var(--code-bg) 85%, white 4%);
}
.code-panel-title {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: #93a2b8;
  letter-spacing: 0.02em;
}
.code-panel pre {
  margin: 0;
  padding: 1rem 1.1rem;
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.88rem;
  line-height: 1.6;
}
.code-output {
  margin: 0;
  padding: 0.9rem 1.1rem;
  border-top: 1px solid var(--code-border);
  background: var(--code-bg);
  color: #d7f7e6;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  white-space: pre-wrap;
  word-break: break-word;
  display: none;
}
.code-output.show { display: block; }
.code-output.is-error { color: #ffb4ac; }

/* keyword highlighting kept intentionally simple: static <span> classes emitted at build time */
.tok-kw { color: #ff7b9c; }
.tok-str { color: #a5e07f; }
.tok-com { color: #7d8ba1; font-style: italic; }
.tok-fn { color: #7fd7ff; }
.tok-type { color: #ffcb6b; }

/* ---------------------------------------------------------------
   Callouts
   --------------------------------------------------------------- */
.callout {
  border-radius: var(--radius);
  padding: 0.95rem 1.1rem;
  margin: 1.4rem 0;
  border: 1px solid var(--border);
  background: var(--bg-raised);
}
.callout-title {
  font-weight: 700;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  display: flex;
  align-items: center;
  gap: 0.5em;
  margin-bottom: 0.35em;
}
.callout p:last-child { margin-bottom: 0; }
.callout-tip { background: var(--accent-bg); border-color: color-mix(in srgb, var(--accent) 35%, var(--border)); }
.callout-tip .callout-title { color: var(--accent-strong); }
.callout-mistake { background: var(--danger-bg); border-color: color-mix(in srgb, var(--danger) 35%, var(--border)); }
.callout-mistake .callout-title { color: var(--danger); }
.callout-ok { background: var(--ok-bg); border-color: color-mix(in srgb, var(--ok) 35%, var(--border)); }
.callout-ok .callout-title { color: var(--ok); }

/* ---------------------------------------------------------------
   Visualization stage (shared shell for all interactive diagrams)
   --------------------------------------------------------------- */
.viz {
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--bg-raised);
  padding: 1.4rem;
  margin: 1.6rem 0;
  box-shadow: var(--shadow);
}
.viz-stage {
  background: var(--bg-sunken);
  border-radius: var(--radius);
  padding: 1.4rem 1rem;
  min-height: 160px;
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 0.6rem;
  overflow: hidden;
}
.viz-controls {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.6rem;
  margin-top: 1rem;
}
.viz-caption {
  font-size: 0.85rem;
  color: var(--text-dim);
  margin-top: 0.7rem;
  min-height: 1.3em;
}
.viz-caption strong { color: var(--text); }

/* goroutine lanes */
.lane-row { display: flex; align-items: center; gap: 0.8rem; }
.lane-label { width: 92px; flex: none; font-family: var(--font-mono); font-size: 0.8rem; color: var(--text-dim); }
.lane-track {
  position: relative;
  flex: 1;
  height: 22px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 999px;
  overflow: hidden;
}
.lane-fill {
  position: absolute; inset: 0; width: 0%;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--gopher-cyan), var(--accent-strong));
  transition: width linear;
}
.lane-done-badge {
  font-size: 0.72rem; font-weight: 700; color: var(--ok);
  width: 78px; flex: none; text-align: right; opacity: 0;
  transition: opacity 0.2s ease;
}
.lane-done-badge.show { opacity: 1; }

/* handshake (unbuffered) */
.hs-track {
  position: relative;
  height: 90px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 10px;
}
.hs-node {
  width: 84px; flex: none;
  display: flex; flex-direction: column; align-items: center; gap: 0.4rem;
  font-size: 0.78rem; color: var(--text-dim); font-family: var(--font-mono);
}
.hs-dot {
  width: 34px; height: 34px; border-radius: 50%;
  background: var(--bg); border: 2px solid var(--border);
  display: flex; align-items: center; justify-content: center;
  transition: all 0.35s ease;
}
.hs-pipe {
  flex: 1; height: 6px; margin: 0 4px; border-radius: 999px;
  background: repeating-linear-gradient(90deg, var(--border) 0 8px, transparent 8px 14px);
  position: relative;
}
.hs-packet {
  position: absolute; top: 50%; left: 6%;
  width: 20px; height: 20px; margin-top: -10px;
  border-radius: 6px;
  background: var(--gopher-cyan);
  box-shadow: 0 0 0 4px var(--accent-bg);
  opacity: 0;
  transition: left 0.6s cubic-bezier(.4,0,.2,1), opacity 0.2s ease;
}
.hs-packet.show { opacity: 1; }
.hs-dot.waiting { border-color: var(--warn); animation: pulse 1s ease-in-out infinite; }
.hs-dot.active { border-color: var(--ok); background: var(--ok-bg); }

@keyframes pulse {
  0%, 100% { box-shadow: 0 0 0 0 color-mix(in srgb, var(--warn) 35%, transparent); }
  50% { box-shadow: 0 0 0 6px transparent; }
}

/* buffered queue */
.queue-row { display: flex; align-items: center; gap: 1.1rem; flex-wrap: wrap; }
.queue-slots { display: flex; gap: 0.5rem; }
.queue-slot {
  width: 46px; height: 46px;
  border: 2px dashed var(--border);
  border-radius: var(--radius-sm);
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-mono); font-weight: 700; font-size: 0.95rem;
  color: var(--text-dim);
  transition: all 0.25s ease;
}
.queue-slot.filled {
  border-style: solid;
  border-color: var(--gopher-cyan);
  background: var(--accent-bg);
  color: var(--accent-strong);
}
.queue-meta { font-family: var(--font-mono); font-size: 0.85rem; color: var(--text-dim); }
.queue-sender {
  display: flex; align-items: center; gap: 0.5rem;
  font-family: var(--font-mono); font-size: 0.8rem; color: var(--text-dim);
}
.queue-sender .hs-dot { width: 30px; height: 30px; }

/* select multiplexer */
.mux-wrap { display: flex; align-items: center; gap: 1.6rem; justify-content: center; flex-wrap: wrap; }
.mux-ch { display: flex; align-items: center; gap: 0.6rem; }
.mux-ch .hs-dot { width: 30px; height: 30px; font-size: 0.75rem; }
.mux-box {
  width: 64px; height: 64px; border-radius: var(--radius);
  border: 2px solid var(--border);
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-mono); font-weight: 700; font-size: 0.72rem;
  color: var(--text-dim); text-align: center;
  transition: all 0.3s ease;
}
.mux-box.picked { border-color: var(--ok); background: var(--ok-bg); color: var(--ok); }
.tally-row { display: flex; gap: 1.4rem; font-family: var(--font-mono); font-size: 0.85rem; }
.tally-bar-track { width: 120px; height: 8px; background: var(--bg); border: 1px solid var(--border); border-radius: 999px; overflow: hidden; display: inline-block; vertical-align: middle; margin-left: 0.5rem; }
.tally-bar-fill { height: 100%; background: var(--gopher-cyan); width: 0%; transition: width 0.25s ease; }

/* ---------------------------------------------------------------
   Roadmap (home page)
   --------------------------------------------------------------- */
.roadmap { display: flex; flex-direction: column; gap: 0.9rem; margin: 2rem 0; }
.roadmap-group { }
.roadmap-group-title {
  font-size: 0.78rem; font-weight: 700; text-transform: uppercase;
  letter-spacing: 0.06em; color: var(--text-dim); margin-bottom: 0.6rem;
}
.roadmap-nodes { display: flex; flex-wrap: wrap; gap: 0.6rem; }
.roadmap-node {
  display: flex; align-items: center; gap: 0.55rem;
  padding: 0.55em 0.9em;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--bg-raised);
  text-decoration: none;
  color: var(--text);
  font-size: 0.88rem;
  font-weight: 600;
  transition: border-color 0.15s ease, transform 0.1s ease;
}
.roadmap-node:hover { border-color: var(--accent); transform: translateY(-1px); }
.roadmap-node .status-dot { width: 8px; height: 8px; border-radius: 50%; background: var(--ok); flex: none; }
.roadmap-node.soon {
  color: var(--text-dim);
  cursor: default;
  border-style: dashed;
}
.roadmap-node.soon:hover { transform: none; border-color: var(--border); }
.roadmap-node.soon .status-dot { background: var(--text-dim); opacity: 0.5; }

.hero-visual { margin: 2rem 0; }

/* ---------------------------------------------------------------
   Basics: annotated code, type boxes, loop step-through, fn flow
   --------------------------------------------------------------- */
.anno {
  cursor: pointer;
  border-bottom: 1px dashed var(--accent);
  transition: background 0.15s ease;
}
.anno:hover, .anno.active { background: var(--accent-bg); }

.type-grid { display: flex; flex-wrap: wrap; gap: 0.8rem; }
.type-box {
  flex: 1; min-width: 130px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.9rem 1rem;
  background: var(--bg);
  text-align: center;
  transition: border-color 0.2s ease;
}
.type-box.active { border-color: var(--gopher-cyan); }
.type-box-name { font-family: var(--font-mono); font-size: 0.78rem; color: var(--accent-strong); font-weight: 700; margin-bottom: 0.5rem; }
.type-box-value { font-family: var(--font-mono); font-size: 1.1rem; font-weight: 700; min-height: 1.4em; }
.type-box-label { font-size: 0.72rem; color: var(--text-dim); margin-top: 0.3rem; }

.loop-row { display: flex; gap: 0.7rem; justify-content: center; flex-wrap: wrap; }
.loop-node { display: flex; flex-direction: column; align-items: center; gap: 0.4rem; }
.loop-dot {
  width: 40px; height: 40px; border-radius: 50%;
  border: 2px solid var(--border);
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-mono); font-weight: 700;
  transition: all 0.25s ease;
}
.loop-dot.current { border-color: var(--gopher-cyan); background: var(--accent-bg); }
.loop-dot.even { border-color: var(--ok); color: var(--ok); }
.loop-dot.odd { border-color: var(--warn); color: var(--warn); }
.loop-tag { font-size: 0.7rem; color: var(--text-dim); min-height: 1.2em; }

.flow-io { display: flex; align-items: center; justify-content: center; gap: 1rem; flex-wrap: wrap; }
.flow-box {
  min-width: 70px; padding: 0.6rem 0.9rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg);
  font-family: var(--font-mono);
  text-align: center; font-weight: 700;
  opacity: 0.35;
  transition: all 0.3s ease;
}
.flow-box.active { opacity: 1; border-color: var(--gopher-cyan); background: var(--accent-bg); }
.flow-fn {
  padding: 0.8rem 1.2rem;
  border-radius: var(--radius);
  border: 2px solid var(--border);
  font-family: var(--font-mono); font-weight: 700;
  transition: all 0.3s ease;
}
.flow-fn.active { border-color: var(--gopher-cyan); background: var(--accent-bg); }
.flow-arrow { color: var(--text-dim); font-size: 1.2rem; }

/* Basics: scope shadowing diagram */
.scope-row { display: flex; gap: 1.5rem; justify-content: center; flex-wrap: wrap; align-items: stretch; }
.scope-block {
  display: flex; flex-direction: column; gap: 0.5rem;
  border: 2px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem 1.2rem;
  background: var(--bg);
  min-width: 190px;
  transition: border-color 0.3s ease;
}
.scope-block-title { font-size: 0.72rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.04em; color: var(--text-dim); }
.scope-var-row {
  font-family: var(--font-mono); font-size: 0.9rem;
  padding: 0.35rem 0.5rem;
  border-radius: var(--radius-sm);
  background: var(--bg-sunken);
  transition: all 0.3s ease;
}
.scope-var-row.shadowed { border-left: 3px solid var(--danger); background: var(--danger-bg); }
.scope-var-row.ok { border-left: 3px solid var(--ok); background: var(--ok-bg); }
.scope-caption { font-size: 0.75rem; color: var(--text-dim); font-family: var(--font-mono); }
.scope-inner {
  border: 2px dashed var(--warn);
  border-radius: var(--radius-sm);
  padding: 0.8rem 1rem;
  margin-top: 0.5rem;
  display: flex; flex-direction: column; gap: 0.4rem;
  background: var(--warn-bg);
  transition: border-color 0.3s ease;
}

/* Basics: for-range decomposition */
.range-row { display: flex; flex-direction: column; align-items: center; gap: 0.6rem; }
.range-code { font-family: var(--font-mono); font-size: 0.88rem; color: var(--accent-strong); font-weight: 700; }
.range-decomp-row { display: flex; gap: 0.5rem; align-items: center; justify-content: center; flex-wrap: wrap; }
.range-decomp-item {
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.5rem 0.8rem;
  background: var(--bg);
  font-family: var(--font-mono); font-size: 0.85rem;
  transition: all 0.3s ease;
  min-width: 50px; text-align: center;
}
.range-decomp-item.key { border-color: var(--accent); background: var(--accent-bg); color: var(--accent-strong); }
.range-decomp-item.val { border-color: var(--ok); background: var(--ok-bg); color: var(--ok); }

/* Basics: defer stack diagram */
.defer-stage {
  display: flex; flex-direction: column; align-items: center; gap: 1rem;
  min-height: 200px;
}
.defer-stack {
  display: flex; flex-direction: column-reverse; gap: 0.35rem;
  border: 2px solid var(--border);
  border-radius: var(--radius);
  padding: 0.7rem;
  background: var(--bg-sunken);
  min-width: 200px; min-height: 140px;
}
.defer-frame {
  padding: 0.4rem 0.8rem;
  border-radius: var(--radius-sm);
  background: var(--bg);
  border: 1px solid var(--border);
  font-family: var(--font-mono); font-size: 0.82rem;
  text-align: center;
  transition: all 0.3s ease;
  opacity: 0;
}
.defer-frame.show { opacity: 1; }
.defer-frame.executing { border-color: var(--warn); background: var(--warn-bg); color: var(--warn); }
.defer-frame.done { border-color: var(--ok); background: var(--ok-bg); color: var(--ok); opacity: 0.5; }
.defer-label { font-size: 0.75rem; font-family: var(--font-mono); color: var(--text-dim); min-height: 1.2em; }

/* Basics: closure capture diagram */
.closure-row { display: flex; gap: 1.5rem; justify-content: center; flex-wrap: wrap; align-items: flex-start; }
.closure-env {
  border: 2px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem 1.2rem;
  background: var(--bg-raised);
  min-width: 160px;
  transition: border-color 0.3s ease;
}
.closure-env-title { font-size: 0.72rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.04em; color: var(--text-dim); margin-bottom: 0.5rem; }
.closure-var {
  font-family: var(--font-mono); font-size: 0.85rem;
  padding: 0.3rem 0.5rem;
  border-radius: var(--radius-sm);
  background: var(--bg);
  transition: all 0.3s ease;
}
.closure-var.captured { border-left: 3px solid var(--accent); background: var(--accent-bg); }
.closure-lens { text-align: center; font-size: 1.2rem; color: var(--text-dim); align-self: center; }
.closure-arrow { color: var(--accent); font-size: 1.5rem; align-self: center; }

/* ---------------------------------------------------------------
   Core: struct boxes, array/slice cells, interface satisfaction
   --------------------------------------------------------------- */
.obj-row { display: flex; gap: 2rem; justify-content: center; flex-wrap: wrap; align-items: flex-start; }
.obj-col { display: flex; flex-direction: column; align-items: center; gap: 0.5rem; }
.obj-col-title { font-size: 0.78rem; font-weight: 700; color: var(--text-dim); text-transform: uppercase; letter-spacing: 0.04em; }
.obj-box {
  padding: 0.7rem 1.1rem;
  border: 2px solid var(--border);
  border-radius: var(--radius);
  font-family: var(--font-mono);
  font-weight: 700;
  background: var(--bg);
  transition: all 0.3s ease;
}
.obj-box.changed { border-color: var(--ok); background: var(--ok-bg); color: var(--ok); }
.obj-box.ghost { opacity: 0.45; border-style: dashed; }
.obj-note { font-size: 0.72rem; color: var(--text-dim); text-align: center; max-width: 160px; }

.array-row { display: flex; gap: 0.35rem; justify-content: center; }
.array-cell {
  width: 44px; height: 44px;
  border: 2px solid var(--border);
  border-radius: var(--radius-sm);
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-mono); font-weight: 700;
  transition: all 0.3s ease;
}
.array-cell.touched { border-color: var(--gopher-cyan); background: var(--accent-bg); }
.array-brackets { display: flex; gap: 0.35rem; justify-content: center; margin-top: 0.4rem; }
.array-bracket-label {
  width: 44px; text-align: center;
  font-family: var(--font-mono); font-size: 0.68rem; color: var(--text-dim);
  visibility: hidden;
}
.array-bracket-label.show-a { visibility: visible; color: var(--accent-strong); }
.array-bracket-label.show-b { visibility: visible; color: var(--warn); }

.sat-row { display: flex; gap: 1.4rem; justify-content: center; flex-wrap: wrap; }
.sat-item { display: flex; flex-direction: column; align-items: center; gap: 0.4rem; font-family: var(--font-mono); font-size: 0.85rem; }
.sat-check { color: var(--ok); font-weight: 700; }

.tv-pair { display: flex; gap: 1.5rem; justify-content: center; flex-wrap: wrap; }
.tv-box { text-align: center; }
.tv-box-label { font-size: 0.72rem; color: var(--text-dim); margin-bottom: 0.4rem; text-transform: uppercase; letter-spacing: 0.04em; }
.tv-box-value {
  padding: 0.7rem 1rem;
  border: 2px solid var(--border);
  border-radius: var(--radius);
  font-family: var(--font-mono); font-weight: 700;
  min-width: 90px;
  transition: all 0.3s ease;
}
.tv-box-value.set { border-color: var(--warn); background: var(--warn-bg); color: var(--warn); }

/* ---------------------------------------------------------------
   Advanced: generics substitution, context cancellation tree
   --------------------------------------------------------------- */
.gen-row { display: flex; align-items: center; justify-content: center; gap: 1rem; flex-wrap: wrap; }
.gen-badge {
  padding: 0.5em 0.9em;
  border-radius: 999px;
  border: 2px solid var(--gopher-cyan);
  background: var(--accent-bg);
  color: var(--accent-strong);
  font-family: var(--font-mono); font-weight: 700; font-size: 0.85rem;
  transition: all 0.2s ease;
}

.ctx-tree { display: flex; flex-direction: column; align-items: center; gap: 0.9rem; }
.ctx-node {
  padding: 0.55em 1em;
  border-radius: var(--radius);
  border: 2px solid var(--border);
  font-family: var(--font-mono); font-size: 0.82rem; font-weight: 700;
  transition: all 0.3s ease;
}
.ctx-node.cancelled { border-color: var(--danger); background: var(--danger-bg); color: var(--danger); }
.ctx-node.gc-deleted {
  opacity: 0.3;
  border-style: dashed;
  text-decoration: line-through;
  color: var(--text-dim);
}
.ctx-children { display: flex; gap: 1.6rem; }
.ctx-branch { display: flex; flex-direction: column; align-items: center; gap: 0.5rem; }
.ctx-line { width: 2px; height: 18px; background: var(--border); }

/* ---------------------------------------------------------------
   Operators: reconcile loop (desired vs actual state)
   --------------------------------------------------------------- */
.recon-row { display: flex; align-items: center; justify-content: center; gap: 1.5rem; flex-wrap: wrap; }
.recon-box {
  min-width: 210px;
  border: 2px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem 1.2rem;
  background: var(--bg);
  transition: border-color 0.3s ease;
}
.recon-box-title { font-size: 0.75rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.04em; color: var(--text-dim); margin-bottom: 0.6rem; }
.recon-field { font-family: var(--font-mono); font-size: 0.85rem; display: flex; justify-content: space-between; gap: 0.8rem; padding: 0.2rem 0; }
.recon-field .val { font-weight: 700; }
.recon-field .val.drift { color: var(--warn); }
.recon-field .val.match { color: var(--ok); }
.recon-loop-icon { font-size: 1.7rem; color: var(--text-dim); transition: transform 0.5s ease, color 0.3s ease; }
.recon-loop-icon.spin { animation: recon-spin 0.6s linear; color: var(--gopher-cyan); }
@keyframes recon-spin { from { transform: rotate(0deg); } to { transform: rotate(360deg); } }

/* ---------------------------------------------------------------
   Interview questions (level-tabbed Q&A)
   --------------------------------------------------------------- */
.interview-tabs {
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--bg-raised);
  padding: 1.4rem;
  margin: 1.6rem 0;
  box-shadow: var(--shadow);
}
.interview-tab-buttons {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-bottom: 1.2rem;
}
.interview-tab-btn {
  font-family: var(--font-sans);
  font-size: 0.88rem;
  font-weight: 600;
  padding: 0.5em 1.15em;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--text-dim);
  cursor: pointer;
  transition: background 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}
.interview-tab-btn:hover { border-color: var(--accent); color: var(--text); }
.interview-tab-btn.active {
  background: var(--gopher-cyan);
  border-color: var(--gopher-cyan);
  color: #04262d;
}
.interview-qa-panel { display: flex; flex-direction: column; gap: 0.8rem; }
.interview-qa-panel[hidden] { display: none; }
.interview-qa-item {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.9rem 1.1rem;
  background: var(--bg);
}
.interview-q {
  font-weight: 700;
  margin: 0 0 0.4em;
  color: var(--text);
}
.interview-a { margin: 0; color: var(--text-dim); }
.interview-a:last-child { margin-bottom: 0; }

/* ---------------------------------------------------------------
   Coding interview questions (category-tabbed problems + solutions)
   --------------------------------------------------------------- */
.coding-tabs {
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  background: var(--bg-raised);
  padding: 1.4rem;
  margin: 1.6rem 0;
  box-shadow: var(--shadow);
}
.coding-tab-buttons {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
  margin-bottom: 1.4rem;
}
.coding-tab-btn {
  font-family: var(--font-sans);
  font-size: 0.88rem;
  font-weight: 600;
  padding: 0.5em 1.15em;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--text-dim);
  cursor: pointer;
  transition: background 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}
.coding-tab-btn:hover { border-color: var(--accent); color: var(--text); }
.coding-tab-btn.active {
  background: var(--gopher-cyan);
  border-color: var(--gopher-cyan);
  color: #04262d;
}
.coding-category-panel { display: flex; flex-direction: column; gap: 1.6rem; }
.coding-category-panel[hidden] { display: none; }
.coding-q-item { }
.coding-q-title {
  font-size: 1.05rem;
  font-weight: 700;
  margin: 0 0 0.5em;
  color: var(--text);
}
.coding-q-desc { margin: 0 0 0.9em; color: var(--text-dim); }
.coding-q-desc:last-child { margin-bottom: 0; }

@media (max-width: 640px) {
  h1 { font-size: 1.7rem; }
  .page, .page-wide { padding: 1.6rem 1.1rem 4rem; }
  .lane-label { width: 64px; font-size: 0.72rem; }
  .hs-node { width: 60px; }
  .nav-links { gap: 0.7rem; }
  .interview-tab-btn { flex: 1 1 auto; text-align: center; }
  .coding-tab-btn { flex: 1 1 auto; text-align: center; }
}