:root {
  color-scheme: light;
  --bg: #f3efe6;
  --panel: #fbf9f4;
  --panel-alt: #f3ede0;
  --panel-border: #e2d9c6;
  --ink: #26221c;
  --ink-dim: #7a715f;
  --accent: #b5502e;
  --accent-ink: #fdf4ed;
  --accent-soft: #f0ddd0;
  --teal: #2f6f68;
  --teal-soft: #dfe9e6;
  --warn: #93650f;
  --warn-soft: #f1e3c4;
  --shadow: 0 1px 2px rgba(38, 34, 28, 0.04), 0 6px 20px rgba(38, 34, 28, 0.05);
  --mono: "SF Mono", "JetBrains Mono", ui-monospace, Menlo, Consolas, monospace;
  --serif: ui-serif, Georgia, "Iowan Old Style", "Times New Roman", serif;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    color-scheme: dark;
    --bg: #1b1814;
    --panel: #242019;
    --panel-alt: #2b261e;
    --panel-border: #3c352a;
    --ink: #ede6d9;
    --ink-dim: #a49a86;
    --accent: #dc8258;
    --accent-ink: #241209;
    --accent-soft: #3a2417;
    --teal: #7fbcb2;
    --teal-soft: #223330;
    --warn: #e0b968;
    --warn-soft: #362c17;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.2), 0 8px 24px rgba(0, 0, 0, 0.25);
  }
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  line-height: 1.5;
}

#app { display: flex; min-height: 100vh; }

#sidebar {
  width: 260px;
  flex-shrink: 0;
  background: var(--panel);
  border-right: 1px solid var(--panel-border);
  display: flex;
  flex-direction: column;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
}
.brand { padding: 18px 16px 6px; }
.brand-title {
  font-family: var(--mono);
  font-size: 17px;
  font-weight: 700;
  letter-spacing: 0.01em;
}
.brand-sub { font-size: 12px; color: var(--ink-dim); margin-top: 4px; line-height: 1.4; }

#module-list { padding: 14px 10px; flex: 1; }
.mod-item {
  display: block;
  width: 100%;
  text-align: left;
  background: none;
  border: none;
  border-radius: 8px;
  padding: 8px 10px;
  font-size: 13.5px;
  color: var(--ink);
  cursor: pointer;
  font-family: var(--sans);
  display: flex;
  align-items: center;
  gap: 8px;
}
.mod-item:hover { background: var(--panel-alt); }
.mod-item.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.mod-num { font-family: var(--mono); font-size: 13px; width: 18px; text-align: center; flex-shrink: 0; }

.sidebar-footer { padding: 10px; border-top: 1px solid var(--panel-border); }
.side-link {
  display: block;
  width: 100%;
  text-align: left;
  background: none;
  border: none;
  padding: 8px 10px;
  font-size: 13px;
  color: var(--ink-dim);
  cursor: pointer;
  text-decoration: none;
  border-radius: 8px;
  font-family: var(--sans);
}
.side-link:hover { background: var(--panel-alt); color: var(--ink); }

#main {
  flex: 1;
  padding: 32px 40px 80px;
  max-width: 980px;
}

.module-header { margin-bottom: 14px; }
.module-num-label {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--accent);
  margin-bottom: 4px;
}
.module-header h1 { font-family: var(--serif); font-size: 28px; margin: 0; }

.module-intro {
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 14px;
  box-shadow: var(--shadow);
  padding: 18px 22px;
  font-size: 14.5px;
  line-height: 1.65;
  margin-bottom: 20px;
}
.module-intro p { margin: 0 0 12px; }
.module-intro p:last-child { margin-bottom: 0; }
.module-intro code {
  background: var(--panel-alt);
  padding: 1px 5px;
  border-radius: 4px;
  font-family: var(--mono);
  font-size: 0.9em;
}
.module-intro pre {
  background: var(--panel-alt);
  border: 1px solid var(--panel-border);
  border-radius: 8px;
  padding: 12px 14px;
  overflow-x: auto;
  font-family: var(--mono);
  font-size: 12.5px;
  line-height: 1.5;
}

.card {
  background: var(--panel);
  border: 1px solid var(--panel-border);
  border-radius: 14px;
  box-shadow: var(--shadow);
  padding: 18px 22px;
  margin-bottom: 16px;
}
.card h2 { font-family: var(--serif); margin: 0 0 4px; font-size: 17px; }
.card .help { margin-top: 0; font-size: 13px; color: var(--ink-dim); }
.card code { background: var(--panel-alt); padding: 1px 5px; border-radius: 4px; font-family: var(--mono); font-size: 0.9em; }

.teaching-block {
  margin: 0 0 16px;
  padding: 14px 16px;
  border-radius: 8px;
  background: var(--panel-alt);
  border: 1px solid var(--panel-border);
  border-left: 3px solid var(--teal);
  font-size: 13.5px;
  line-height: 1.6;
}
.teaching-block p { margin: 0 0 10px; }
.teaching-block p:last-child { margin-bottom: 0; }
.teaching-block pre { background: rgba(0,0,0,0.06); padding: 10px 12px; border-radius: 6px; overflow-x: auto; margin: 8px 0; }
.teaching-block code { background: rgba(0,0,0,0.06); padding: 1px 4px; border-radius: 4px; font-family: var(--mono); }
.teaching-label {
  font-family: var(--sans);
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--teal);
  margin-bottom: 8px;
}

.meta-row { margin-top: 10px; font-size: 13px; }
.meta-row strong { color: var(--ink-dim); font-weight: 600; margin-right: 4px; }
.meta-row code { background: rgba(0,0,0,0.06); padding: 1px 5px; border-radius: 4px; font-family: var(--mono); font-size: 0.92em; margin-right: 2px; }

.inline-link { color: var(--accent); text-decoration: none; font-family: var(--mono); }
.inline-link:hover { text-decoration: underline; }

.pill {
  display: inline-block;
  font-size: 10.5px;
  font-family: var(--mono);
  padding: 2px 8px;
  border-radius: 20px;
  background: var(--panel-alt);
  color: var(--ink-dim);
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

/* structure diagram */
.graph-wrap { margin-top: 12px; }
.graph { max-width: 100%; width: 100%; }
.graph-node { cursor: pointer; }
.graph-node rect { transition: stroke 0.12s ease; }
.graph-node:hover rect { stroke: var(--accent); }

/* step-by-step walkthrough */
.step-card {
  display: flex;
  gap: 14px;
  padding: 16px 18px;
  border-radius: 10px;
  background: var(--panel-alt);
  border: 1px solid var(--panel-border);
  margin-bottom: 12px;
}
.step-num {
  font-family: var(--mono);
  font-size: 20px;
  font-weight: 700;
  color: var(--accent);
  flex-shrink: 0;
  width: 28px;
}
.step-body h3 { margin: 0 0 4px; font-size: 14.5px; font-family: var(--sans); }
.step-call { font-family: var(--mono); font-size: 12px; color: var(--ink-dim); margin-bottom: 8px; }
.step-body p { margin: 0; font-size: 13.5px; line-height: 1.6; }
.step-file-link { color: var(--accent); font-family: var(--mono); font-size: 12px; text-decoration: none; }
.step-file-link:hover { text-decoration: underline; }

/* file list */
.file-list { display: flex; flex-direction: column; gap: 8px; margin-top: 4px; }
.file-item {
  display: flex;
  flex-direction: column;
  gap: 2px;
  text-align: left;
  width: 100%;
  background: var(--panel-alt);
  border: 1px solid var(--panel-border);
  border-radius: 8px;
  padding: 10px 14px;
  cursor: pointer;
  font-family: var(--sans);
}
.file-item:hover { border-color: var(--accent); }
.file-name { font-family: var(--mono); font-weight: 700; font-size: 13px; color: var(--ink); }
.file-summary { font-size: 12.5px; color: var(--ink-dim); }

/* code viewer */
.fn-name { font-family: var(--mono); font-size: 12px; color: var(--ink-dim); margin-bottom: 4px; }
.CodeMirror {
  border: 1px solid var(--panel-border);
  border-radius: 8px;
  font-family: var(--mono);
  font-size: 12.5px;
  height: auto;
}
.code-source .CodeMirror-scroll { max-height: 70vh; }

::selection { background: var(--accent-soft); }

@media (max-width: 800px) {
  #app { flex-direction: column; }
  #sidebar { position: relative; width: 100%; height: auto; }
  #main { padding: 20px; }
}