*,
*:before,
*:after {
  box-sizing: border-box;
}

body {
    margin: 0;
    height: 100vh;
    background-color: darkgrey;
    display: flex;
    align-items: center;
    justify-content: center;
}

th, td {
  width: 20px;
  text-align: center;
}

.backgroundColorGrey {
  background-color: grey;
}