Not bad at all,but needs inprovement
First,stuff with blood:P You dont need to spit whole screen with red when something hits player,it confuses when u have heavy battle at hand.
Second,yeah im gonna start yaping bout weapons and ammo.
As previouse guy stated,dont short our arsenal to 1 weapone at time.Also,give more ammo power ups,otherwise its easy to run dry even at 3rd wave.Another thing,I figure out u want this game to be a challenge,since u put online score,but give some medi-packs,otherwise when run out of ammo -ur toasted.Overal good game,and music rocks!!:D
Ps - maybe consider adding power ups to player stats as speed,fire rate and so?;] Good luck