html, body {
    height: 100%;
}

body {
    margin: 0;
    font: 16px sans-serif;
}

.container {
    position: relative;
    display: flex;
    height: 100%;
    flex-direction: column;
}

.label {
    position: absolute;
    display: flex;
    align-items: center;
    justify-content: center;
    left: 0;
    top: 0;
    right: 0;
    bottom: 0;
    padding: 20px;
    margin: 20px;
    border: 3px dashed #aaa;
    border-radius: 10px;
    font-size: 120%;
}

.container_hidden .label {
    display: none;
}

.container_drag .label {
    display: flex;
    border-color: #444;
}

.preview-item {
    display: inline-block;
    vertical-align: bottom;
    margin: 10px;
}

.preview-item__label {
    text-align: center;
}