button {
  height: 50px;
  background-color: rgb(102, 115, 119);
  color: white;
  border: none;
  font-size: 24px;
  font-family: 'B612 Mono', 'Courier New', Courier, monospace;
  text-align: center;
  float: right;
}

.correct {
  border: 5px solid;
  border-color: green;
}

.incorrect {
  border: 5px solid;
  border-color: red;
}

table {
  margin:1em auto;
  color: #2E3436;
  border: 5px solid;
  border-color: transparent;
}

table:first-child {
  border-top-width: 10px;
}

td {
  height:30px;
  width:30px;
  border:1px solid;
  text-align:center;
}
td:first-child {
  border-left:solid;
  border-left-width: 10px;
}
td:nth-child(3n) {
  border-right:solid ;
  border-right-width: 10px;
}
tr:first-child {
  border-top:solid;
  border-top-width: 10px;
}

tr:nth-child(3n) td {
  border-bottom:solid ;
  border-bottom-width: 10px;
}
input {
  width: 50px;
  height: 50px;
  background-color: rgb(102, 115, 119);
  color: white;
  border: none;
  font-size: 24px;
  font-family: 'B612 Mono', 'Courier New', Courier, monospace;
  text-align: center;
  caret-color: transparent;
}

input:focus {
  background-color: #729FCF;
}

/* Chrome, Safari, Edge, Opera */
input::-webkit-outer-spin-button,
input::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

/* Firefox */
input[type=number] {
  -moz-appearance: textfield;
}

input:disabled {
  background-color: rgb(66, 75, 78);
}