.btn-group button {
    background-color: #4CAF50; /* Green background */
    border: 1px solid green; /* Green border */
    color: white; /* White text */
    cursor: pointer; /* Pointer/hand icon */
    float: left; /* Float the buttons side by side */
}

.btn-group button:not(:last-child) {
    border-right: none; /* Prevent double borders */
}

.btn-group button:focus {
    background-color: #3e8e41;
}

.control-button {
    width: 16.6%;
    height: 100%;
    font-size: 3em;
}