* {
  box-sizing: border-box;
}

table {
  border-collapse: collapse;
  border-spacing: 0;
}

main {
  display: flex;
  width: max-content;
  margin: auto;
  flex-direction: column;
}
main > :first-child {
  margin-bottom: 24px;
}

h1 {
  font-size: 1.25rem;
  margin: 8px 0;
}

.cell {
  border: 1px solid #eee;
}
.cell-alive {
  background: #bbb;
}