@charset"UTF-8";

main {
    width: 800px;
    margin: 0 auto;
}

ul {
    padding: 0;
    list-style: none;
    width: calc(10em*3 + 30px);
    margin: 0px auto;
    display: flex;
    justify-content: space-between;

}

li {
    width: 10em;

    background-color: aqua;
    border: solid blue 2px;
    text-align: center;
}

li a {
    text-decoration: none;
    display: block;
    padding: 5px 0;
}

li a:hover {
    background-color: #0f0;
}