Actually bigger enemies are easier to kill as they move slow.... 1 point and 5 point enemies are really annoying, and they are supposed to be the weaker ones....
That's a good retro game, one that really remember of old games.... old graphs.... no crazy powerups, nothing is new there, and in retro games, that's good. 4/5 cuz u should put an level generator with automatically increases level difficulty, so there'll be infinite levels