:root {
    --body-bg-dark:     #030812;
    --text-light:       #e0e8f0;
    --link-bg-dark:     #0d192b;
    --link-text-light:  #e0e8f0;
}

/* main page */
body {
    background: var(--body-bg-dark);
    font-family: sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;      /* vh = viewport height */
    margin: 0;
    padding: 1rem;          /* 1 root em = relative to root font (~16px) */
}

h1 {
    color: var(--text-light);
    font-size: 2rem;
    text-align: center;
    margin-bottom: 2rem;
}

ul {
    list-style: none;
    padding: 0;
    text-align: center;
}

li {
    margin: 2rem 0;         /* top/bottom = 2rem, left/right = 0 */
}

ul a,
.button {
    color: var(--link-text-light);
    background: var(--link-bg-dark);
    text-decoration: none;  /* removes underline from link */
    padding: 0.75rem 1.5rem;
    border-radius: 2rem;
}