upload-images/css/upload_images.css

[data-target="upload-images.input"] {
    width: 0.1px;
    height: 0.1px;
    opacity: 0;
    overflow: hidden;
    position: absolute;
    z-index: -1;
}
[data-target="upload-images.input"] + label {
    font-size: 1.25em;
    font-weight: 700;
    color: white;
    background-color: black;
    display: inline-block;
    padding: 1rem;
}
[data-target="upload-images.input"]:focus + label,
[data-target="upload-images.input"] + label:hover {
    background-color: red;
}
[data-target="upload-images.input"] + label {
    cursor: pointer; /* "hand" cursor */
}
[data-target="upload-images.input"]:focus + label {
    outline: thin dotted;
    outline: -webkit-focus-ring-color auto 5px;
}
[data-target="upload-images.input"]:focus-within + label {
    outline: thin dotted;
    outline: -webkit-focus-ring-color auto 5px;
}
[data-target="upload-images.input"] + label * {
    pointer-events: none;
}

[data-target="upload-images.output"] img {
    max-width: 30rem;
}
[data-target="upload-images.output"].oversized {
    background: red;
    height: 4rem;
    padding: 1rem 2rem;
}

[data-target="upload-images.dropzone"] {
    border: 5px solid black;
    margin: 2rem auto;
    min-width: 30rem;
}
[data-target="upload-images.dropzone"].hidden {
    display: none;
}
[data-target="upload-images.dropzone"]:hover,
[data-target="upload-images.dropzone"].active {
    border-color: red;
    cursor: pointer; /* "hand" cursor */
}

[data-target="upload-images.submit"] {
    width: 30rem;
    font-size: 2rem;
}