webaudio.css

#audio-drop-zone {
    user-select: none;
    display: flex;
    margin-top: 30px;
    border: 1px dashed black;
    aspect-ratio: 1 / 0.5;
    align-items: center;
    justify-content: center;
}

#audio-drop-zone:hover {
    background-color: rgba(0, 0, 0, 0.1);
}

#audio-drop-zone > span {
    transition: opacity 250ms ease;
    opacity: 1.0;
}

#audio-drop-zone.dropping > span {
    opacity: 0;
}

#files > div {
    display: flex;
    column-gap: 5px;
    margin: 5px 0;
}

#files > div > div:last-child {
    margin-left: auto;
}
#files > div > div.channel-selector {
    display: flex;
}
#files > div > div.channel-selector > input {
    display: block;
    width: 30px;
}