:root {
  --fg: #1d1f23;
  --muted: #5a6068;
  --bg: #fafbfc;
  --panel: #ffffff;
  --border: #d8dde3;
  --accent: #1f6feb;
  --accent-fg: #ffffff;
  --error: #b3261e;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  font-family: -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--fg);
  font-size: 15px;
  line-height: 1.5;
}

header {
  max-width: 980px;
  margin: 0 auto;
  padding: 32px 24px 8px;
}

h1 {
  font-size: 1.55rem;
  font-weight: 600;
  margin: 0 0 6px;
}

.subtitle {
  color: var(--muted);
  margin: 0 0 16px;
  max-width: 700px;
}

main {
  max-width: 980px;
  margin: 0 auto;
  padding: 8px 24px 64px;
}

.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  align-items: flex-end;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 16px;
  margin-bottom: 16px;
}

.control {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.control label {
  font-size: 0.85rem;
  color: var(--muted);
  font-weight: 500;
}

select {
  padding: 6px 8px;
  font-size: 0.95rem;
  border: 1px solid var(--border);
  border-radius: 4px;
  background: white;
  min-width: 140px;
}

select:disabled, button:disabled {
  opacity: 0.55;
  cursor: not-allowed;
}

button {
  background: var(--accent);
  color: var(--accent-fg);
  border: none;
  border-radius: 4px;
  padding: 8px 18px;
  font-size: 0.95rem;
  font-weight: 500;
  cursor: pointer;
}

button:hover:not(:disabled) {
  filter: brightness(1.05);
}

.status {
  padding: 10px 14px;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 0.92rem;
  color: var(--muted);
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
  white-space: pre-wrap;
  margin-bottom: 16px;
  min-height: 1.2em;
}

.status.error { color: var(--error); }

.output {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 16px;
}

.output h2 {
  margin: 0 0 12px;
  font-size: 1.05rem;
  font-weight: 600;
}

canvas {
  display: block;
  width: 100%;
  height: auto;
  background: #eef0f3;
  image-rendering: pixelated;
  border-radius: 4px;
}

#colorbar {
  margin-top: 6px;
  background: transparent;
  image-rendering: auto;
}

.vmax {
  margin: 4px 0 0;
  font-size: 0.85rem;
  color: var(--muted);
  text-align: center;
}

.about {
  margin-top: 24px;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px 16px;
}

.about summary {
  cursor: pointer;
  font-weight: 500;
}

.about p {
  margin-top: 10px;
  color: var(--fg);
}