pico.chat/pico.css

body {
    margin: 0;
    padding: 0;
}
.chat {
    display: grid;
    grid-template-areas:
        'posts online'
        'actions actions'
        'media media'
    ;
    grid-template-columns: 1fr auto;
    grid-template-rows: 140px auto auto;

    position: fixed;
    top: 0;

    --pad: 3px;
    padding: var(--pad);
    width: calc(100vw - 2 * var(--pad));
}
.ts {
    color: rgba(0, 0, 0, 0.4);
    font-family: monospace;
}
.source {
    font-weight: bold;
}
.online {
    grid-area: online;
}
.posts {
    grid-area: posts;
    overflow-y: scroll;
}
.post .text p {
    margin: 0;
}
.post .text p:first-child {
    display: inline;
}
.actions {
    grid-area: actions;
    display: grid;
    grid-template-columns: 1fr auto;
}
.media {
    grid-area: media;
}
#textbox {
    resize: vertical;
}
.post > div {
    display: inline;
    padding-left: var(--pad);
}
.videos {
    display: inline-grid;
    grid-auto-flow: column;
    --gap: 1em;
    grid-gap: var(--gap);
    padding: var(--gap);
    overflow: hidden;
    resize: both;
    height: 200px;
}
.video-container {
    background-color: lightsteelblue;
    display: inline-block;
    position: relative;
    overflow: scroll;
}
.video-meta {
    position: absolute;
    z-index: 999;
}
.video-option {
    display: block;
}
.video-container:not(.visible) {
    display: none;
}
.video-container.square {
    height: 100%;
    width: var(--height);
    overflow: hidden;
}
.video-container.square video {
    object-fit: cover;
    width: 100%;
    height: 100%;
}
.video-container.mirror video {
    transform: scaleX(-1);
}
@media only screen and (min-width: 800px) {
    .chat {
        grid-template-areas:
            'online media'
            'posts media'
            'actions media'
        ;
        grid-template-columns: 1fr 4fr;
        grid-template-rows: auto 1fr auto;
        height: 100vh;
        width: 100vw;
    }
}