body {
  padding: 0;
  margin: 0;
  background: #333;
  color: black;
}
main {
  width: 100%;
  height: 100%;
  display: grid;
  position: fixed;
  grid-template-rows: 50px auto;
  gap: 2px;
}
header {
  background: darksalmon;
  font-family: Impact, Haettenschweiler, "Arial Narrow Bold", sans-serif;
  padding: 12px 20px;
}
header button {
  height: 26px;
  font-size: 14px;
  line-height: 1em;
  padding: 4px 0.6em;
  margin: 0;
  text-transform: uppercase;
  vertical-align: middle;
}
section {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr 1fr 1fr 1fr 1fr 1fr;
  grid-template-rows: 1fr 1fr 1fr 1fr;
  gap: 2px;
}
section button {
  border: none;
  margin: 0;
  padding: 0;
  background: snow;
}
section button:hover {
  background: lightgray;
}
section button.active,
section button:active {
  background: darkgray;
}