#right-panel {
    display: flex;
    flex-direction: column;
    position: fixed;
    right: 0;

    width: calc(2 * var(--unit-size-w));
    padding: var(--small-size);
    box-sizing: border-box;

    font-size: var(--medium-size);
    background-image: linear-gradient(var(--bg1), transparent);
}

.icon-attach {
    width: var(--main-size);
    height: var(--main-size);
    font-size: var(--medium-size);
    fill: var(--fg);
    cursor: pointer;
}

#replyform {
    margin: var(--small-size);
}
#replyform div {
    display: inline-flex;
    justify-content: flex-start;
    width: 100%;
    box-sizing: border-box;
}
#replyform div textarea {
    width: 100%;
}

/* UNTOGGLED */
.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-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;
}