body {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 100vh;
    margin: 0;
    background-color: #000; /* pure black background */
}

.clock {
    /* scale font using viewport width so it adapts to mobile */
    font-size: 20vw;
    font-family: 'Courier New', Courier, monospace;
    color: #f0f0f0; /* cooler off-white text color */
    display: flex;
    align-items: center;
    justify-content: center;
    width: 100%;
    height: 100%;
}

#display {
    /* let the parent .clock determine size */
    font-size: 2em;
    font-family: monospace;
    font-weight: bold;
    color: #f0f0f0; /* same off-white color */
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.5);
    margin: 0;
    text-align: center;
}

/* cap size on larger screens */
@media (min-width: 600px) {
    .clock { font-size: 6em; }
}