Play animation in reverse on exiting hover state

a::before{
    content: "🌑";
}
a:hover::before{
    animation: moonPhases 1s forwards;
}
@keyframes moonPhases {
    0%   { content: "🌑"; }
    25%  { content: "🌒"; }
    50%  { content: "🌓"; }
    75%  { content: "🌔"; }
    100% { content: "🌕"; }
}