INSERT COIN

Thrust, turn, shoot. The rocks break into smaller rocks and the smaller ones are faster. A saucer comes looking for you, and after a few waves it is the one that aims.

They come down a row at a time and speed up as you thin them out, so the game gets harder precisely because you are winning. Your shelters wear away where anyone shoots them, including you.

You are the exterminator. Clear every spider and every egg sac, then leave by the door. The thread always comes down before the spider does, which is the only warning you get.