Wasn't too bad. I found it best to upgrade the shotgun to max then upgrade the machine gun till the rocket launcher becomes unlocked and then max it till the last weapon is unlocked and then buy and max that one. After that I was able to max out everything else. I did find one bug with the last stage when fighting the boss if you hit the s key to bring up the weapon/wall menu it brings up a you escaped from this town screen and the game ends.

Decent game. Sort of easy once you figure out the upgrade process. Just upgrade the next available weapon and its game over for the zombies! It also becomes rather systematic after the first few levels. Fun game though.

Can't pass 3rd stage to many zombies at one time.

Not bad. I discovered a glitch that made me extra money though, so it kind of made the difficulty not so drastic. As a word to other players, I would encourage you to immediately invest in whatever the next weapon is, regardless of how well you've upgraded the previous one EXCEPT for the sniper rifle. It proves almost useless against the thicker hordes; the rocket launcher is a better investment.

Again, DO NOT waste your time on the sniper rifle, fellow players. The reload time is too lengthy, and shots do not penetrate multiple enemies.

Nice game, though quite routine. It gets too difficult sometimes IMO, when too many zombies are swarming your wall it seems you just can't aim properly so you wound many and kill none... and then lose. It appears necessary to make the "correct" balance between upgrading the existing weapons, getting specific new ones, and upgrading the wall in order to make it. Given that, it's a clear downside that there's no information what upgrading a weapon would do - increase ammunition? damage? fire rate?
Also, a small thing often missed - allow muting the game anywhere, i.e. while shopping or when paused, not only while shooting around.
I did kinda like the graphics. Not the hero with his cigar and blue eyes and "I'm cool" expression, but the silly zombies yes, especially the ones banging their heads at my wall :)