body {
  font-family: Helvetica, sans-serif;
  display: flex;
  flex-direction: column;
  margin: 0;
  padding: 1rem;
  box-sizing: border-box;
  user-select: none;
}
h1 { font-size: 1.2em; font-weight: normal; }
h1 code { font-size: 1.2em; }
a, a:link, a:visited, a:focus, a:hover { color: #333; }
header { padding-bottom: 1rem; font-size: 0.85em; }
canvas {
  box-sizing: border-box;
  touch-action: none;
  width: 100%;
  height: 100%;
  border: 1px solid #999;
  background: #f9f9f9;
}