Decent.
I didn't had the glitch were zombies got stuck, however I had immense screen lag due to the insane amount of zombies that are present between the levels 20-30 ( I had blood and shake off, and low quality ).
I almost most died @ level 30 due to simpely to much zombies, the boss didn't even touch me.
I have some suggestions for a possible sequal:
- Less zombies, but stronger ones ( screen lag ).
- A storyline ( strongly suggested :-p )
- Not a plain gunshop, but use a scavage hunt, for example, for better guns, medical supplies, armour etc etc...
- Make it less repetative.
Overall a decent game, but certainly alot of room for improvement, I hope you make a part two, good luck!