I really like this genre, still, maybe a few more upgrades and it would be good to go. Maybe another type of enemy that shoots at the player or something. For upgrades, you could implement something like a multi-shot, each level giving one extra bullet per shot. Upgrade for projectile velocity, maybe a shield to protect the motherboard too. I dont know, but plenty of ways to keep expanding, you could try to keep on working on it and little by little add new simple ideas to it. But i like it, got to wave 11 shite.