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

button {
    border: none;
    padding: 10px;
    margin: 10px;
}

button.active {
    background-color: red;
    color: white;
}

li {
    border: 1px solid #333;
    padding: 10px;
}

li a {
    color: blue;
}

@media screen and (max-width: 768px) {
    button {
        font-size: 14px;
    }    
}