table, th, td { border: 1px solid black; border-collapse: collapse; }
th { width: 40px; height: 40px; font-size: x-large; text-align: center; color: black; }
.left { border-left-width: 3px; }
.right { border-right-width: 3px; }
.top { border-top-width: 3px; }
.bottom { border-bottom-width: 3px; }
button { margin-top: 1rem; }
em { font-size: small; }