* {
    outline: none;
    box-sizing: border-box;
}

html,
body {
    height: 100%;
    margin: 0;
    padding: 0;
}

body {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    align-items: center;
    font-family: sans-serif;
}

main {
    padding: 1rem;
    max-width: 40rem;
}

footer {
    width: 100%;
    background: lightgray;
    border-top: 1px solid gray;
    padding: 0.5rem;
}

a,
a:link,
a:visited {
    color: navy;
    text-decoration: none;
}

a:hover {
    text-decoration: underline;
}

a:active {
    color: red;
}

div.tool {
    margin: 0.5rem 0;
    padding: 0.5rem;
    border-radius: 0.5rem;
}