main {
  width: 20em;
  margin: 0px auto;
}

h1 {
  text-align: center;
}

#canvas {
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  grid-template-rows: repeat(8, 1fr);
}

.cell {
  width: 2.5em;
  height: 2.5em;
  box-sizing: border-box;
  border: 1px dashed dodgerblue;
}

.cell.filled {
  background-color: black;
}

fieldset {
  margin: 2em 0;
}