#display {
    margin: auto;
    border: 2px solid black;
    width: 300px;
    text-align: center;
    font-weight: bold;
    font-size: 30px;
}

button {
    border: 3px solid black;
    background: white;
    margin: 3px;
    width: 92px;
    height: 50px;
    cursor: pointer;
    transition: all .1s;
}

button:focus {
    outline: none;
}

.keypress {
    background: yellowgreen;
    border-color: brown;
    box-shadow: 0px 0px 20px brown;
    font-weight: bold;
}