.pin-input {
    font-family: monospace;
    font-size: 2.5rem;
    border: none;
    outline: none;
    padding: 0;
    width: calc(1.6ch * 4);
    background: repeating-linear-gradient(90deg, dimgrey 0, dimgrey 1ch, transparent 0, transparent 1.6ch) 0 100%/100% 2px no-repeat;
    color: dimgrey;
    letter-spacing: .6ch;
}

/* Don't collapse dd when there is no data */
dd:empty::before {
    content: '\00a0';  /* Unicode for non-breaking space */
}