2/5, because of how repetitive the levels are. Needs upgrades, more bad guys, etc. Would be 3/5, but it is so easy to die while the hearts fall and then miss them. What would be better is if every time you're hit, your ragdoll would just flash or something, and you wouldn't actually die until your hearts ran out, so you could keep playing even if you got shot, and wouldn't have to wait.