:root {
  --ink: #2b2b38;
  --muted: #6b6b7a;
  --red: #e23b3b;
  --blue: #4f8cff;
}

* { box-sizing: border-box; }

body.viz-page {
  margin: 0;
  min-height: 100vh;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  color: var(--ink);
  background: linear-gradient(160deg, #fdf6ec 0%, #e9f3fb 100%);
  padding: 16px 20px;
}

.back {
  position: relative;
  display: inline-block;
  margin-bottom: 12px;
  text-decoration: none;
  color: var(--ink);
  font-weight: 600;
  padding: 8px 14px;
  border-radius: 999px;
  background: #fff;
  box-shadow: 0 4px 14px rgba(43, 43, 56, 0.1);
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.back:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(43, 43, 56, 0.16);
}

.viz-wrap {
  max-width: 1200px;
  margin: 0 auto;
}

.viz-header { text-align: center; margin-bottom: 12px; }

.viz-header h1 {
  margin: 0;
  font-size: clamp(1.6rem, 3.5vw, 2.2rem);
  letter-spacing: -0.02em;
}

.viz-header .hint {
  margin: 8px auto 0;
  max-width: 720px;
  color: var(--muted);
  line-height: 1.5;
}

.canvas-card {
  background: #fff;
  border-radius: 18px;
  padding: 12px;
  box-shadow: 0 8px 24px rgba(43, 43, 56, 0.12);
}

#road {
  display: block;
  width: auto;
  max-width: 100%;
  max-height: 52vh;
  margin: 0 auto;
}

.controls {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  margin: 14px 0 0;
  background: #fff;
  padding: 12px 16px;
  border-radius: 16px;
  box-shadow: 0 6px 18px rgba(43, 43, 56, 0.08);
}

.slider-group { display: flex; flex-direction: column; gap: 6px; }

.slider-group label {
  font-weight: 600;
  font-size: 0.92rem;
}

.slider-row { display: flex; align-items: center; gap: 12px; }

.slider-row input[type="range"] { width: 170px; accent-color: var(--blue); }

.slider-row output {
  min-width: 34px;
  text-align: center;
  font-weight: 700;
  background: #eef3fb;
  border-radius: 8px;
  padding: 3px 6px;
}

.buttons { display: flex; flex-wrap: wrap; gap: 10px; }

.btn {
  font: inherit;
  cursor: pointer;
  border: none;
  padding: 12px 18px;
  border-radius: 12px;
  font-weight: 700;
  color: #fff;
  transition: transform 0.12s ease, filter 0.12s ease;
}

.btn:hover { transform: translateY(-2px); filter: brightness(1.05); }
.btn:active { transform: translateY(0); }

.btn-brake { background: var(--red); }
.btn-reset { background: var(--blue); }

.slider-ticks {
  display: flex;
  justify-content: space-between;
  width: 170px;
  margin-top: 2px;
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--muted);
}

.slider-ticks span { cursor: default; opacity: 0.55; }
.slider-ticks span.active { opacity: 1; color: var(--blue); }

.slider-group input[type="range"]#speed { width: 170px; }

.explain {
  margin-top: 12px;
  background: #fff;
  border-radius: 16px;
  box-shadow: 0 6px 18px rgba(43, 43, 56, 0.08);
}

.explain summary {
  cursor: pointer;
  padding: 16px 20px;
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--ink);
  list-style: none;
  display: flex;
  align-items: center;
  gap: 10px;
}

.explain summary::-webkit-details-marker { display: none; }

.explain summary::before {
  content: "▸";
  transition: transform 0.15s ease;
  color: var(--blue);
}

.explain[open] summary::before { transform: rotate(90deg); }

.explain .body {
  padding: 0 20px 18px;
}

.explain hr {
  margin: 0 0 14px;
  border: none;
  border-top: 1px solid #eee;
}

.explain p { line-height: 1.6; color: var(--muted); margin: 0 0 12px; }
.explain p:last-child { margin-bottom: 0; }
.explain strong { color: var(--ink); }

@media (max-width: 640px) {
  body.viz-page { padding: 12px; }
  .controls { flex-direction: column; align-items: stretch; }
  .buttons { justify-content: center; }
  .slider-group input[type="range"], .slider-group input[type="range"]#speed { width: 100%; }
  .slider-ticks { width: 100%; }
}