html, body {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100%;
  overflow: hidden;
  background-color: #e6f3ec; /* page background, unrelated */
}

/* center canvas absolutely */
#town {
  position: fixed;
  left: 50%;
  top: 50%;
  transform: translate(-50%, -50%);

  width: 1000px;
  height: 800px;
}