gnu-social/public/assets/css/right/right.css

.arrow {
    border: solid var(--fg);
    border-width: 0 3px 3px 0;
    display: none;
    padding: 0.3em;
}
.right {
    transform: rotate(135deg);
    -webkit-transform: rotate(135deg);
}

#right-panel {
    display: flex;
    flex-direction: column;
    position: fixed;

    right: 0;
    top: var(--unit-size);
    margin: 0;
}

/* UNTOGGLED */
#right-container {
    right: 0;
    top: 0;
    transition: 0.3s ease;
}
.arrow label {
    display: block;
    cursor: pointer;
}
#toggle-right {
    position: absolute;
    z-index: 2;
    cursor: pointer;
    opacity: 0;
}
#toggle-right:not(:checked)+.arrow {
    transform: rotate(135deg);
    transition: 0.3s ease;
}

/* TOGGLED */
#toggle-right:checked~#right-container {
    display: flex;
    right: 0;
    top: 0;
    transition: 0.3s ease;
}
#toggle-right:checked+.arrow {
    transform: rotate(-45deg);
    transition: 0.3s ease;
}