:root {
  --bg: #0b0f13;
  --card: #141b22;
  --card-border: #232f3a;
  --ink: #e8eef2;
  --muted: #8fa1ad;
  --accent: #7bd88f;
  --accent2: #ff9f7b;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: ui-sans-serif, system-ui, "Segoe UI", Roboto, sans-serif;
}

body {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 32px 16px 48px;
}

header {
  max-width: 720px;
  text-align: center;
  margin-bottom: 20px;
}

h1 {
  font-size: 2.4rem;
  margin: 0 0 8px;
  letter-spacing: -0.02em;
}

.accent { color: var(--accent); }

.tagline {
  color: var(--muted);
  margin: 0 auto 12px;
  max-width: 60ch;
  line-height: 1.5;
}

.explainer {
  text-align: left;
  background: var(--card);
  border: 1px solid var(--card-border);
  border-radius: 10px;
  padding: 10px 14px;
  color: var(--muted);
  font-size: 0.92rem;
}

.explainer summary {
  cursor: pointer;
  color: var(--ink);
  font-weight: 600;
}

.explainer p { line-height: 1.55; margin: 10px 0 2px; }

.explainer code {
  background: #1c2731;
  padding: 1px 6px;
  border-radius: 5px;
}

.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
  justify-content: center;
  margin: 14px 0 24px;
  max-width: 900px;
}

.control {
  display: flex;
  flex-direction: column;
  gap: 4px;
  font-size: 0.85rem;
  color: var(--muted);
  min-width: 160px;
}

.control input[type="range"] { accent-color: var(--accent); }

select {
  background: var(--card);
  color: var(--ink);
  border: 1px solid var(--card-border);
  border-radius: 8px;
  padding: 6px 8px;
  font-size: 0.9rem;
}

.btn {
  background: var(--card);
  color: var(--ink);
  border: 1px solid var(--card-border);
  border-radius: 8px;
  padding: 9px 14px;
  font-size: 0.9rem;
  cursor: pointer;
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: border-color 0.15s ease, transform 0.1s ease;
}

.btn:hover { border-color: var(--accent); }
.btn:active { transform: scale(0.97); }

.btn.primary {
  background: var(--accent);
  color: #0b1a10;
  border-color: var(--accent);
  font-weight: 600;
}

.dragHint {
  color: var(--muted);
  font-size: 0.82rem;
  text-align: center;
  margin: 0 0 14px;
}

main {
  width: 100%;
  display: flex;
  justify-content: center;
}

#grid {
  display: grid;
  gap: 14px;
  justify-content: center;
}

.knot-card {
  background: var(--card);
  border: 1px solid var(--card-border);
  border-radius: 14px;
  padding: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
}

.knot-card canvas {
  display: block;
  width: 100%;
  height: 100%;
  border-radius: 8px;
}

footer {
  margin-top: 36px;
  color: var(--muted);
  font-size: 0.85rem;
  text-align: center;
}

footer a { color: var(--muted); }
footer a:hover { color: var(--accent); }

@media (max-width: 480px) {
  h1 { font-size: 1.9rem; }
  .control { min-width: 130px; }
}