:root {
  --canvas-size: 600px;
}

body {
  font-family: system-ui, "Noto Sans JP", sans-serif;
  display: flex;
  flex-direction: column;
  align-items: center;
  margin: 0;
  padding: 1rem;
  background: #fafafa;
}

h1 { 
  margin: 0 0 0.5rem; 
  font-size: 1.4rem; 
}

#controls {
  display: flex;
  gap: 0.8rem;
  flex-wrap: wrap;
  margin-bottom: 0.8rem;
}

#controls label { 
  font-size: 0.9rem; 
}

#controls input[type="number"] {
  width: 5rem;
  padding: 0.2rem 0.4rem;
  font-size: 0.9rem;
}

button {
  padding: 0.4rem 0.8rem;
  font-size: 0.9rem;
  border: none;
  border-radius: 4px;
  cursor: pointer;
  background: #1976d2;
  color: #fff;
}

button:disabled { 
  background: #90caf9; 
  cursor: not-allowed; 
}

canvas {
  border: 1px solid #b0bec5;
  width: var(--canvas-size);
  height: var(--canvas-size);
  max-width: 100%;
  touch-action: manipulation;
  background: #ffffff;
}

/* 小さな表示用の説明 */
#note { 
  font-size: 0.8rem; 
  color: #555; 
  margin-top: 0.6rem; 
}