#daynight {
    position: absolute;
    left: 50%; top: 1rem; width: 4rem; height: 4rem;
    border-radius: 0.8rem;
    z-index: 4;
}

body:not(.started) #daynight {
    opacity: 0;
    pointer-events: none;
}

body:not(.started) #daynight button {
    pointer-events: none;
}

#daynight button {
    width: 4rem; height: 4rem; line-height: 4rem;
    background-color: rgba(0,0,0,0.7);
    border: 0;
    border-radius: 0.8rem;
    transition: background-color 0.2s;
    pointer-events: all;
    cursor: pointer;
}

#daynight button img {
    position: absolute;
    left: 50%; top: 50%; height: 100%; width: 100%;
    transform: translate(-50%,-50%) scale(0);
    opacity: 0;
    transition: transform 0.3s, opacity 0.3s;
}

#daynight.day button img.day {
    transform: translate(-50%,-50%) scale(1);
    opacity: 1;
}

#daynight.night button img.night {
    transform: translate(-50%,-50%) scale(1);
    opacity: 1;
}