body {
    width: 200px;
}

button {
    height: 30px;
    width: 30px;
    outline: none;
    border-radius: 2px;
    cursor: pointer;
    border: 1px solid currentColor;

}

button:active {
    background-color: currentColor;
}

button.current {
    box-shadow: 0 0 0 2px white,
        0 0 0 4px black;
}

h1, h2 {
    font-size: 1rem;
    margin: 8px 0;
}

ul {
    margin: 0;
    padding: 0;
    list-style: none;
}