SingleFile/extension/ui/pages/editor.css

html,
body {
    height: 100%;
}

body {
    margin: 0;
    display: flex;
    flex-direction: column;
    user-select: none;
}

.toolbar {
    background-color: #425c69;
    border-bottom: 1px solid #6d6d6d;
}

img[type=button] {
    margin-left: 1px;
    margin-right: 1px;
    margin-top: 5px;
    margin-bottom: 4px;
    opacity: .75;
    cursor: pointer;
}

img[type=button]:hover {
    opacity: 1;
}

img[type=button].edit-disabled,
img[type=button].highlight-disabled,
img[type=button].remove-highlight-disabled {
    opacity: .25;
}

img[type=button].edit-disabled:hover,
img[type=button].highlight-disabled:hover,
img[type=button].remove-highlight-disabled:hover {
    opacity: .5;
}

.buttons {
    display: inline-block;
}

.separator {
    display: inline-block;
    width: 2px;
    height: 22px;
    background-color: #9ab0bb;
    margin-left: 2px;
    margin-right: 2px;
    margin-top: 1px;
    margin-bottom: 4px;
}

.editor {
    flex: auto;
    border: none;
}

@media (max-width: 420px) {
    .separator {
        display: none;
    }
}

@media (orientation: portrait) {
    body {
        flex-direction: row;
    }

    .toolbar {
        max-width: 32px;
        border-bottom: 0px;
        border-right: 1px solid #6d6d6d;
    }

    .separator {
        margin-left: 4px;
        width: 22px;
        height: 2px;
    }

    img[type="button"] {
        margin-left: 4px;
        margin-bottom: 1px;
    }

    @media (max-height: 495px) {
        .separator {
            display: none;
        }
    }
}