body {
  margin: 0;
  font-family: Arial, sans-serif;
  text-align: center;
  background: #f4f4f4;
}

h1 {
  margin: 10px;
}

.toolbar {
  margin-bottom: 10px;
}

button {
  padding: 10px 15px;
  margin: 5px;
  font-weight: bold;
  cursor: pointer;
}

canvas {
  border: 2px solid #333;
  background: white;
  display: block;
  margin: 0 auto;
  touch-action: none;
}