.scroll-up {
    position: fixed;
    bottom: 1rem;
    right: 2rem;
    display: inline-block;
    width: 3.75rem;
    height: 3.75rem;
    border-radius: 50%;
    overflow: hidden;
}

.scroll-up:before {
    content: "\25B2";
    display: block;
    color: white;
    position: absolute;
    font-size: 2.2rem;
    width: 3.75rem;
    height: 3.75rem;
    background: #568eca;
    text-align: center;
    line-height: 3.75rem;
}

.scroll-up__text {
    display: none;
}
.scroll-up {
    font-family: arial, verdana, sans-serif;
    position: fixed;
    bottom: 1rem;
    right: 2rem;
    display: inline-block;
    width: 3.75rem;
    height: 3.75rem;
    border-radius: 50%;
    overflow: hidden;
}

.scroll-up:before {
    content: "\25B2";
    display: block;
    color: white;
    position: absolute;
    font-size: 2.2rem;
    width: 3.75rem;
    height: 3.75rem;
    background: #568eca;
    text-align: center;
    line-height: 1.6;
}

.scroll-up__text {
    display: none;
}
Update css to work better with Firefox
Update css to work better with Firefox

The widget css was a bit off with firefox (compared to chrome).
Problem was the line height and the default font that was set.

This is fixed by specifying a font family (seems that both arial &
verdana are cross-platform) and use e relative line height instead of a
rem unit.
