The premise of this game is cool, less defense = more attack, but sadly it isn't balanced: having more attack is always a better option than having more defense (defence is only usefull with the explosive bird imo) for one simple reason: increasing the attack also increases your speed, and having more speed means dodging attacks/escaping enemies more eastly, thus taking overall less damage, while on the other hand if you increase defense your speed also drops making it harder to escape/dodging enemies thus taking overall more damage
Another things is the corpses: there were some times where i wanted to shoot at an enemy behind a corpse and the corpse was basically a meat shield for the enemy. Also the corpses can be easily mistaken for an alive enemy from far away (especially when you have low health), and when there is a bunch of enemies in the room is really hard to see who is alive and who is not without getting too close (but in doing that you put yourself at risk of taking damage, and when you have 1/2 of defense that's a huge risk that usually isn't worth doing)
Overall this is a great game!! Good Job!!