space to shoot mouse to aim
Normal: The green guy, he's a three-shot Fast: Wave 2, better act fast but its 2-shot Slow: Wave 4, slow but 4-shot Boss: Wave 6, Your average boss, 12-shot Summoner: Wave 8, Summons every 5 seconds, 20-shot Healer: Wave 11, Heals enemies to the max, 32-shot
