style.css

*{
    margin: 0;
}

body {
    background-color: rgb(51, 50, 51);
    font-family: 'Open Sans', sans-serif;
    color: white;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 100vh;
  }

  h1{
    text-align: center;
    margin-top: 72px;
  }

.content{
    width: 100%;
    display: flex;
    margin-top: 72px;
    justify-content: center;
    position: relative;
}

table {
    border-collapse: collapse;}

tr{
    height: 100px;
    width: 100px
}

td {
    border: 5px solid white;
    padding: 10px;
    width: 100px;
    height: 100px;
    text-align: center;
    vertical-align: middle;
    font-size: 24px;
}

td:hover{
    background: rgba(255, 255, 255, .3);
    cursor: pointer;
}

table tr:first-child td {
    border-top: 0;
  }

  table tr td:first-child {
    border-left: 0;
  }

  table tr:last-child td {
    border-bottom: 0;
  }
  
  table tr td:last-child {
    border-right: 0;
  }

  button{
    margin-top: 48px;
    padding: 16px 32px;
    border-radius: 5px;
    border: none;
    background: rgb(203, 200, 203);
    color: rgb(51, 50, 51);
  }

  button:hover{
    opacity: .8;
    cursor: pointer;
  }