/* ============ theme ============ */
:root {
  color-scheme: light;
  --page: #f9f9f7;
  --surface: #fcfcfb;
  --ink: #0b0b0b;
  --ink-2: #52514e;
  --muted: #898781;
  --grid: #e1e0d9;
  --axis: #c3c2b7;
  --border: rgba(11, 11, 11, 0.10);
  --accent: #2a78d6;   /* series 1 blue   */
  --accent2: #eb6834;  /* series 2 orange */
  --accent3: #1baf7a;  /* series 3 aqua   */
  --accent-wash: rgba(42, 120, 214, 0.12);
  --accent2-wash: rgba(235, 104, 52, 0.14);
  --accent3-wash: rgba(27, 175, 122, 0.16);
  --shadow: 0 8px 28px rgba(11, 11, 11, 0.10);
}
@media (prefers-color-scheme: dark) {
  :root:where(:not([data-theme="light"])) {
    color-scheme: dark;
    --page: #0d0d0d;
    --surface: #1a1a19;
    --ink: #ffffff;
    --ink-2: #c3c2b7;
    --muted: #898781;
    --grid: #2c2c2a;
    --axis: #383835;
    --border: rgba(255, 255, 255, 0.10);
    --accent: #3987e5;
    --accent2: #d95926;
    --accent3: #199e70;
    --accent-wash: rgba(57, 135, 229, 0.20);
    --accent2-wash: rgba(217, 89, 38, 0.22);
    --accent3-wash: rgba(25, 158, 112, 0.24);
    --shadow: 0 8px 28px rgba(0, 0, 0, 0.5);
  }
}
:root[data-theme="dark"] {
  color-scheme: dark;
  --page: #0d0d0d;
  --surface: #1a1a19;
  --ink: #ffffff;
  --ink-2: #c3c2b7;
  --muted: #898781;
  --grid: #2c2c2a;
  --axis: #383835;
  --border: rgba(255, 255, 255, 0.10);
  --accent: #3987e5;
  --accent2: #d95926;
  --accent3: #199e70;
  --accent-wash: rgba(57, 135, 229, 0.20);
  --accent2-wash: rgba(217, 89, 38, 0.22);
  --accent3-wash: rgba(25, 158, 112, 0.24);
  --shadow: 0 8px 28px rgba(0, 0, 0, 0.5);
}

/* ============ base ============ */
* { box-sizing: border-box; }
html { height: 100%; }
body {
  margin: 0;
  min-height: 100%;
  background: var(--page);
  color: var(--ink);
  font: 16px/1.6 system-ui, -apple-system, "Segoe UI", sans-serif;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
h1, h2, h3 { font-family: Georgia, "Times New Roman", serif; font-weight: 500; line-height: 1.25; }
code { font-family: ui-monospace, "SF Mono", Menlo, monospace; font-size: 0.9em; }

.wrap { max-width: 1080px; margin: 0 auto; padding: 0 24px 96px; }
.narrow { max-width: 880px; }

/* ============ header ============ */
header.site {
  display: flex; align-items: baseline; gap: 16px;
  padding: 28px 0 8px;
}
header.site .brand {
  font-family: Georgia, serif; font-size: 20px; color: var(--ink);
}
header.site .brand:hover { text-decoration: none; }
header.site .spacer { flex: 1; }
button.theme-toggle {
  border: 1px solid var(--border); background: var(--surface); color: var(--ink-2);
  border-radius: 999px; padding: 4px 14px; font: inherit; font-size: 13px; cursor: pointer;
}
button.theme-toggle:hover { color: var(--ink); }

/* ============ home ============ */
.hero { padding: 40px 0 12px; max-width: 720px; }
.hero h1 { font-size: 44px; margin: 0 0 12px; }
.hero p { color: var(--ink-2); font-size: 17px; margin: 0 0 10px; }
.hero .fine { font-size: 14.5px; color: var(--muted); }

.grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 18px; margin-top: 34px;
}
.card {
  display: block; background: var(--surface); border: 1px solid var(--border);
  border-radius: 12px; padding: 20px 20px 18px; color: var(--ink);
  transition: transform .12s ease, box-shadow .12s ease;
}
.card:hover { text-decoration: none; transform: translateY(-2px); box-shadow: var(--shadow); }
.card .glyph { height: 84px; margin-bottom: 12px; }
.card .glyph svg { height: 100%; width: auto; display: block; }
.card h3 { margin: 0 0 4px; font-size: 20px; }
.card .tagline { color: var(--ink-2); font-size: 14.5px; margin: 0; }
.chip {
  display: inline-block; font-size: 12px; letter-spacing: .02em; color: var(--muted);
  border: 1px solid var(--border); border-radius: 999px; padding: 1px 10px; margin: 0 6px 8px 0;
}

/* ============ theorem page ============ */
.crumb { margin: 26px 0 0; font-size: 14px; }
.crumb a { color: var(--muted); }
.thm-head { padding: 18px 0 6px; }
.thm-head h1 { font-size: 38px; margin: 0 0 6px; }
.thm-head .meta { color: var(--muted); font-size: 14px; margin-bottom: 8px; }
.thm-head .tagline { color: var(--ink-2); font-size: 17px; max-width: 700px; }

.panel {
  background: var(--surface); border: 1px solid var(--border); border-radius: 12px;
  padding: 22px 26px; margin: 22px 0;
}
.panel > h2 {
  font-size: 14px; font-family: system-ui, sans-serif; font-weight: 600;
  letter-spacing: .09em; text-transform: uppercase; color: var(--muted);
  margin: 0 0 14px;
}
.statement-math { padding: 6px 0 2px; overflow-x: auto; }
.statement-math .katex-display { margin: 8px 0 14px; }
.statement-prose { color: var(--ink-2); font-size: 15.5px; }
.statement-prose .katex { font-size: 1.02em; }

/* hoverable terms */
dfn[data-term] {
  font-style: normal; cursor: help;
  border-bottom: 1px dashed var(--accent); color: var(--ink);
}
.tooltip {
  position: fixed; z-index: 40; max-width: 340px;
  background: var(--surface); border: 1px solid var(--border); border-radius: 10px;
  box-shadow: var(--shadow); padding: 12px 14px; font-size: 14px; line-height: 1.5;
  color: var(--ink-2); pointer-events: none;
}
.tooltip b { color: var(--ink); }

/* ============ widget chrome ============ */
.widget { margin: 0; }
.w-intro { color: var(--ink-2); font-size: 15px; margin: 0 0 14px; }
.w-toolbar {
  display: flex; flex-wrap: wrap; gap: 10px 14px; align-items: center;
  margin-bottom: 14px; font-size: 13.5px;
}
.w-toolbar .label { color: var(--muted); font-size: 12.5px; }
.seg { display: inline-flex; border: 1px solid var(--border); border-radius: 8px; overflow: hidden; }
.seg button {
  border: 0; background: transparent; color: var(--ink-2); font: inherit; font-size: 13px;
  padding: 5px 12px; cursor: pointer; border-right: 1px solid var(--border);
}
.seg button:last-child { border-right: 0; }
.seg button.on { background: var(--accent-wash); color: var(--ink); font-weight: 600; }
.btn {
  border: 1px solid var(--border); background: transparent; color: var(--ink-2);
  font: inherit; font-size: 13px; border-radius: 8px; padding: 5px 14px; cursor: pointer;
}
.btn:hover { color: var(--ink); border-color: var(--muted); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
input[type="range"] { accent-color: var(--accent); }

.w-stage {
  position: relative; border: 1px solid var(--border); border-radius: 10px;
  background: var(--page); overflow: hidden;
}
.w-stage canvas, .w-stage svg { display: block; width: 100%; height: auto; touch-action: none; }
.w-caption { color: var(--muted); font-size: 13.5px; margin: 12px 2px 0; }
.readouts {
  display: flex; flex-wrap: wrap; gap: 8px 22px; margin-top: 12px;
  font-size: 14px; color: var(--ink-2);
}
.readouts .v { font-variant-numeric: tabular-nums; color: var(--ink); font-weight: 600; }
.legend { display: flex; gap: 18px; align-items: center; font-size: 13px; color: var(--ink-2); margin-top: 10px; }
.legend .sw { display: inline-block; width: 12px; height: 12px; border-radius: 3px; vertical-align: -1px; margin-right: 6px; }
.legend .ln { display: inline-block; width: 16px; height: 2.5px; border-radius: 2px; vertical-align: 3px; margin-right: 6px; }

/* ============ proof steps ============ */
.pstep {
  border: 1px solid var(--border); border-radius: 10px; margin: 10px 0;
  background: color-mix(in srgb, var(--surface) 60%, var(--page));
}
.pstep summary {
  cursor: pointer; padding: 13px 16px; list-style: none; display: flex; gap: 12px;
}
.pstep summary::-webkit-details-marker { display: none; }
.pstep summary .num {
  flex: none; width: 24px; height: 24px; border-radius: 50%; margin-top: 2px;
  background: var(--accent-wash); color: var(--accent); font-size: 13px; font-weight: 700;
  display: flex; align-items: center; justify-content: center;
}
.pstep summary .head b { display: block; color: var(--ink); font-weight: 600; }
.pstep summary .head span { color: var(--ink-2); font-size: 14.5px; }
.pstep summary .twist { flex: none; color: var(--muted); align-self: center; transition: transform .15s; }
.pstep[open] summary .twist { transform: rotate(90deg); }
.pstep .body {
  padding: 2px 18px 16px 52px; color: var(--ink-2); font-size: 15px;
}
.pstep .body p { margin: 8px 0; }
.note {
  border-left: 3px solid var(--accent2); padding: 4px 14px; margin: 16px 0 4px;
  color: var(--ink-2); font-size: 14.5px;
}
.note b { color: var(--ink); }

/* ============ context chips ============ */
.ctx { display: flex; flex-wrap: wrap; gap: 24px; }
.ctx .col { min-width: 200px; }
.ctx h4 { margin: 0 0 8px; font-size: 12.5px; letter-spacing: .08em; text-transform: uppercase; color: var(--muted); font-weight: 600; }
.ctx a.chip { color: var(--accent); border-color: color-mix(in srgb, var(--accent) 35%, transparent); }
.ctx a.chip:hover { text-decoration: none; background: var(--accent-wash); }

footer.site { margin-top: 60px; color: var(--muted); font-size: 13.5px; border-top: 1px solid var(--border); padding-top: 18px; }

@media (max-width: 640px) {
  .hero h1 { font-size: 34px; }
  .thm-head h1 { font-size: 30px; }
  .panel { padding: 18px 16px; }
  .pstep .body { padding-left: 18px; }
}