It might not be the first but my oldest memory of playing a game was a very old pc game that I can't remember much about and I've never been able to actually find anything about it anywhere. All I remember is that it was a game that had colored rats on conveyor belts and you had to sort them. I'm pretty sure it had a top down perspective as the conveyor belts would loop back to where the rats came from.
Yeah that's it. Also, I think I know why I couldn't find anything about it, it's because it's part of a pack of games and not a stand-alone game. It's also weird that I don't remember any of the other games from that collection.