* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    border-spacing: 0;
}

.sudoku-solver {
    margin: auto;
    width: 50%;
}

.intro {
    font-size: 35px;
    letter-spacing: 1px;
    margin: 30px 0px 10px 0px;
}

.puzzle {
    width: 540px;
    height: 540px;
}

.puzzle input {
    text-align: center;
    font-size: 30px;
    width: 60px;
    height: 60px;
    border: 1px #808080 solid;
}

.odd-section {
    background: #d3d3d3;
}

.solve-button, .clear-button {
    margin-top: 20px;
    background-color: black;
    border: none;
    border-radius: 3px;
    color: white;
    padding: 10px 20px;
    text-align: center;
    text-decoration: none;
    display: inline-block;
    font-size: 18px;
    letter-spacing: 1px;
    cursor: pointer;
}

.clear-button {
    margin-left: 15px;
}

/* Hides up & down arrows from input numbers */
/* 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;
}