That would be cool. There are not so many 4-player-simultan games and the game-principle of alot games are also not really suitable, for having four player sprites on the screen at the same time. It's completely different here in "1nvader", where it would be very useful, as there are only a few enemies on the screen. You could then snatch points from each other, based on the motto - who of the four players aims most accurately and shoots the enemy the most often and the fastest. I think, this could really be fun. By the way, not all 4-player-adapters are wired exactly the same. In my opinion, the Protovision 4-player-adapter seems to be the model, that is most widely used meanwhile. You could then base your decision on that. This could then be used as a guide for the game, when integrating 4-player-gameplay.