style.css

@import url('https://fonts.googleapis.com/css?family=Roboto');

* {
  font-family: 'Roboto', sans-serif;
}

body {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  font-size: 15px;
}

.matrix {
  margin: 20px 0;
}

.matrix__input {
  margin: 3px;
  padding: 3px;
  height: 40px;
  width: 40px;
  text-align: center;
  box-sizing: border-box;
  background: #ccc;
  border: none;
  border-radius: 3px;
  cursor: pointer;
  transition: all .1s ease-in-out;
}

.matrix__input:hover {
  background: #eee;
}

.matrix__input:focus {
  outline: none;
}

.matrix__input-active {
  background: rgba(46, 204, 113, 0.65);
  border: 2px solid rgb(39, 174, 96);
}

.DFS-table {
  width: 60%;
}

.DFS-table tr {
  width: 100%;
  background: rgba(192, 57, 43, .15);
}

.DFS-table tr:nth-child(2n) {
  background: rgba(192, 57, 43, .75);
  color: #fff;
}

.DFS-table td {
  font-size: 1.13rem;
  padding: 5px;
  height: 100%;
  width: 33.3%;
  text-align: center;
}

.input {
  font-size: 1.3rem;
  padding: 5px 10px;
  text-align: center;
  width: 220px;
  height: 45px;
  border: none;
  border-bottom: 2px solid rgb(192, 57, 43);
  margin: 10px 0;
  box-sizing: border-box;
}

.input:focus {
  outline: none;
}

.button {
  font-size: 1.05rem;
  padding: 5px 10px;
  text-align: center;
  width: 220px;
  height: 45px;
  background: none;
  border: 2px solid rgb(192, 57, 43);
  border-radius: 3px;
  margin-bottom: 10px;
  cursor: pointer;
  transition: all .15s ease-in-out;
  perspective: 800px;
}

.button:hover {
  transform: scale(1.07);
}

.button:focus {
  outline: none;
  box-shadow: inset 0 0 10px rgba(192, 57, 43, .5);
}