do not buy more size increases after you reached invulnerabillity, first you can only shoot if you jump, then only at the peak of the jump and eventually you can longer shoot at all happened wave 60 for me
I did but others might not share that as it got a slow start and its more about how to cheese it for me, my robot went super saiyan and became unstoppable by wave 15 (shots blotting out the sky) and invincible(my shots being bigger than my hit aura) by 25
