:root {
  --serif: 'Source Serif 4', Georgia, serif;
  --sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --mono: 'JetBrains Mono', 'SFMono-Regular', Menlo, monospace;

  --bg: #fdfcf9;
  --paper: #ffffff;
  --text: #2f2a22;
  --muted: #6e665b;
  --border: #e2d8c6;
  --accent: #2c6fb7;
  --warm: #d9622b;
  --truth: #1e7770;
  --pred: #d9622b;
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; font-family: var(--serif); color: var(--text); background: var(--bg); line-height: 1.65; }

.article { max-width: 980px; margin: 0 auto; padding: 2.5rem 1.5rem 5rem; }
.back-link { display: inline-block; margin-bottom: 1.5rem; color: var(--muted); text-decoration: none; font-family: var(--sans); font-size: 0.9rem; }
.back-link:hover { color: var(--text); }
.article-header { margin-bottom: 3rem; text-align: center; }
.kicker { margin: 0 0 0.75rem; font-family: var(--sans); font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.14em; color: var(--muted); }
h1 { margin: 0 auto 1rem; font-size: clamp(2.3rem, 5vw, 3.4rem); line-height: 1.1; letter-spacing: -0.02em; color: #1a1815; max-width: 18ch; }
.abstract { margin: 0 auto 1rem; max-width: 62ch; font-size: 1.15rem; color: #4d463d; }
.byline { display: flex; gap: 1rem; justify-content: center; flex-wrap: wrap; margin-top: 1.4rem; padding-top: 1rem; border-top: 1px solid var(--border); color: var(--muted); font-family: var(--sans); font-size: 0.92rem; }

.step-section {
  position: relative; margin-top: 4rem; padding: 3rem 2.5rem;
  background: var(--paper); border: 1px solid var(--border);
  border-radius: 24px; box-shadow: 0 8px 30px rgba(0, 0, 0, 0.03);
}
.step-badge {
  position: absolute; top: -16px; left: 32px;
  background: var(--accent); color: white;
  font-family: var(--sans); font-weight: 700; font-size: 0.85rem;
  text-transform: uppercase; letter-spacing: 0.08em;
  padding: 0.4rem 1.2rem; border-radius: 999px;
  box-shadow: 0 4px 12px rgba(44, 111, 183, 0.25);
}

h2 { margin: 0 0 1rem; font-size: clamp(1.6rem, 3.5vw, 2.2rem); line-height: 1.15; color: #1a1815; }
h3 { margin-top: 2rem; margin-bottom: 0.8rem; font-size: 1.25rem; color: #1a1815; }
p { max-width: 68ch; font-size: 1.1rem; }
code { font-family: var(--mono); font-size: 0.92em; background: rgba(0,0,0,0.05); padding: 0.2em 0.4em; border-radius: 6px; }

.button-row { display: flex; gap: 0.6rem; flex-wrap: wrap; margin: 1rem 0 0.5rem; }
.mode-button {
  border: 1px solid var(--border); background: white; color: var(--text);
  padding: 0.5rem 0.9rem; border-radius: 999px;
  font: 600 0.85rem var(--sans); cursor: pointer;
  transition: all 150ms ease; box-shadow: 0 2px 8px rgba(0,0,0,0.02);
}
.mode-button:hover { transform: translateY(-2px); box-shadow: 0 4px 12px rgba(0,0,0,0.06); border-color: var(--accent); }
.mode-button.is-active { background: var(--text); color: white; border-color: var(--text); }

.action-btn {
  border: none; background: var(--text); color: white;
  padding: 0.6rem 1.1rem; border-radius: 10px;
  font: 600 0.9rem var(--sans); cursor: pointer;
  transition: all 150ms ease;
  box-shadow: 0 4px 14px rgba(0,0,0,0.1);
}
.action-btn:hover { transform: translateY(-2px); background: #1a1815; }
.action-btn:disabled { opacity: 0.5; cursor: not-allowed; transform: none; }
.action-btn--ghost { background: white; color: var(--text); border: 1px solid var(--border); box-shadow: none; }
.action-btn--ghost:hover { background: #f5f0e5; color: var(--text); }
.action-btn--small { padding: 0.4rem 0.9rem; font-size: 0.82rem; }

.control-row { display: grid; grid-template-columns: 1fr 1fr; gap: 1.2rem; margin: 1rem 0; }
.control-block { background: #faf7ef; border: 1px solid var(--border); border-radius: 12px; padding: 1rem 1.2rem; }
.control-block label {
  display: flex; justify-content: space-between; align-items: baseline;
  font-family: var(--sans); font-size: 0.9rem; font-weight: 600;
  color: var(--muted); text-transform: uppercase; letter-spacing: 0.06em;
  margin-bottom: 0.5rem;
}
.control-block label span {
  font-family: var(--mono); font-size: 1rem; color: var(--text);
  font-weight: 700; text-transform: none; letter-spacing: 0;
}
.control-block input[type="range"] { width: 100%; accent-color: var(--accent); }

.toggle-btn {
  padding: 0.5rem 1rem; border-radius: 999px;
  border: 1px solid var(--border); background: white;
  color: var(--muted); font: 600 0.82rem var(--sans);
  cursor: pointer; transition: all 150ms ease;
}
.toggle-btn:hover { border-color: var(--accent); color: var(--text); }
.toggle-btn.is-active { background: var(--accent); color: white; border-color: var(--accent); }

.photo-picker {
  display: grid; grid-template-columns: 2fr 1fr; gap: 1rem;
  align-items: stretch; margin: 1rem 0 1.5rem;
}
@media (max-width: 680px) { .photo-picker { grid-template-columns: 1fr; } }

.upload-zone {
  background: #faf7ef; border: 2px dashed var(--border);
  border-radius: 14px; padding: 1.2rem;
  display: flex; flex-direction: column; gap: 0.5rem; justify-content: center; align-items: center;
  text-align: center; font-family: var(--sans); color: var(--muted);
  transition: all 150ms ease;
  min-height: 120px;
}
.upload-zone.drag-over { border-color: var(--accent); background: #e2eaf5; color: var(--accent); }
.upload-zone strong { color: var(--text); font-size: 0.95rem; }
.upload-zone small { font-size: 0.8rem; }
.upload-zone input[type="file"] { display: none; }

.sample-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 0.5rem; }
@media (max-width: 480px) { .sample-grid { grid-template-columns: repeat(2, 1fr); } }
.sample-thumb {
  background: #faf7ef; border: 2px solid var(--border);
  border-radius: 10px; padding: 0.4rem 0.25rem;
  font-family: var(--sans); font-size: 0.78rem; font-weight: 600;
  color: var(--muted); cursor: pointer; text-align: center;
  transition: all 150ms ease;
  min-height: 54px; display: flex; flex-direction: column; align-items: center; justify-content: center;
}
.sample-thumb:hover { border-color: var(--accent); background: white; }
.sample-thumb.is-active { border-color: var(--text); background: white; color: var(--text); }

.model-status {
  display: inline-flex; align-items: center; gap: 0.5rem;
  padding: 0.35rem 0.7rem; border-radius: 999px;
  font: 600 0.82rem var(--sans);
  background: #faf7ef; border: 1px solid var(--border); color: var(--muted);
  margin-left: 0.5rem;
}
.model-status.is-loading { background: rgba(44, 111, 183, 0.08); color: var(--accent); border-color: rgba(44, 111, 183, 0.2); }
.model-status.is-ready { background: rgba(30, 119, 112, 0.08); color: var(--truth); border-color: rgba(30, 119, 112, 0.3); }
.model-status.is-error { background: rgba(200, 50, 50, 0.08); color: #c03030; border-color: rgba(200, 50, 50, 0.3); }
.model-status .dot { width: 8px; height: 8px; border-radius: 50%; background: currentColor; }
.model-status.is-loading .dot { animation: pulse 1s infinite; }
@keyframes pulse { 0%,100% { opacity: 0.4; } 50% { opacity: 1; } }

.interactive-figure {
  margin: 1.5rem 0; padding: 1.25rem;
  background: white; border: 1px solid var(--border);
  border-radius: 18px; box-shadow: 0 8px 30px rgba(0, 0, 0, 0.04);
}
canvas { display: block; max-width: 100%; height: auto; margin: 0 auto; }
.seg-canvas { border-radius: 8px; background: #222; cursor: crosshair; }

.image-stage-wrap { position: relative; width: 100%; max-width: 720px; margin: 0 auto; }
.image-stage-wrap canvas { width: 100%; height: auto; }

figcaption { margin-top: 0.8rem; color: var(--muted); font-size: 0.9rem; text-align: center; font-family: var(--sans); }

.split-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 1.5rem; align-items: start; }
.split-grid--2-1 { grid-template-columns: 2fr 1fr; }

.math-block { margin: 1.2rem 0; text-align: center; overflow-x: auto; }

.callout { margin: 1.5rem 0; padding: 1rem 1.2rem; border-radius: 0 12px 12px 0; font-size: 1rem; }
.callout strong { font-family: var(--sans); font-size: 0.9rem; }
.callout--think { border-left: 3px solid var(--accent); background: rgba(44, 111, 183, 0.04); }
.callout--warn  { border-left: 3px solid var(--warm);   background: rgba(217, 98, 43, 0.04); }

.explanation-list { max-width: 68ch; font-size: 1.08rem; padding-left: 1.5rem; }
.explanation-list li { margin-bottom: 0.7rem; }

.stat-strip { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 1rem; margin: 1rem 0 0.5rem; }
.stat-pill { background: white; border: 1px solid var(--border); border-radius: 14px; padding: 0.9rem 1rem; text-align: center; }
.stat-label { display: block; margin-bottom: 0.3rem; font-family: var(--sans); font-size: 0.72rem; text-transform: uppercase; letter-spacing: 0.1em; color: var(--muted); }
.stat-value { font: 700 1.5rem var(--mono); color: var(--text); line-height: 1; }
.stat-pill--truth .stat-value { color: var(--truth); }
.stat-pill--pred  .stat-value { color: var(--pred); }
.stat-pill--big .stat-value { font-size: 2rem; }

.misconception-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 1rem; margin: 1.5rem 0; }
.misconception-card { padding: 1.2rem; border: 1px solid rgba(200, 50, 50, 0.15); border-radius: 14px; background: rgba(200, 50, 50, 0.03); }
.misconception-card p { margin: 0; font-size: 0.95rem; line-height: 1.55; }
.misconception-icon {
  display: inline-flex; align-items: center; justify-content: center;
  padding: 0.2rem 0.8rem; border-radius: 16px;
  background: rgba(200, 50, 50, 0.1); color: #c03030;
  font-family: var(--sans); font-size: 0.82rem; font-weight: 700;
  text-transform: uppercase; letter-spacing: 0.05em; margin-bottom: 0.5rem;
}

.examples-table-wrap { overflow-x: auto; margin: 1.5rem 0; }
.examples-table { width: 100%; border-collapse: collapse; font-family: var(--sans); font-size: 0.95rem; }
.examples-table th, .examples-table td { padding: 0.8rem 1rem; text-align: left; border-bottom: 1px solid var(--border); }
.examples-table th { background: rgba(0,0,0,0.02); color: var(--muted); font-weight: 700; text-transform: uppercase; letter-spacing: 0.05em; font-size: 0.82rem; }

.reveal-card {
  background: #1a1815; color: white; border-radius: 22px;
  padding: 2rem; text-align: center; margin: 2rem 0 1rem;
  box-shadow: 0 20px 50px rgba(0,0,0,0.12);
}
.reveal-card h3 { margin: 0 0 0.4rem; font-size: 1.2rem; font-weight: 500; color: #e2d8c6; }
.reveal-number { font: 700 2.6rem var(--sans); color: #ffc266; line-height: 1.1; }
.reveal-card p { margin: 0.8rem auto 0; max-width: 56ch; color: #c8beae; font-size: 1rem; }

.label-chip {
  display: inline-flex; align-items: center; gap: 0.4rem;
  padding: 0.25rem 0.6rem; border-radius: 999px;
  background: white; border: 1px solid var(--border);
  font: 600 0.82rem var(--sans);
  margin-right: 0.3rem; margin-bottom: 0.3rem;
}
.label-chip .swatch { width: 10px; height: 10px; border-radius: 50%; }

.brush-toolbar { display: flex; gap: 0.5rem; flex-wrap: wrap; align-items: center; margin: 0.5rem 0; }

@media (max-width: 880px) {
  .split-grid, .split-grid--2-1, .control-row, .stat-strip { grid-template-columns: 1fr; }
}
@media (max-width: 640px) {
  .article { padding-inline: 1rem; }
  .step-section { padding: 2rem 1.5rem; }
}