You've got a very good game here Jenkem, ranging from the difficulty of the game, to the music and sound effects.
First, I like how at the opening there's a "Day #(randomnumberhere)", it's wonderful. It gives you an actual sense that there was a zombie apocalypse and it has lasted that long.
Second, your game has no regular to major bugs as far as I can tell. The bugs present are very very minor though (Life bars at the top lane are blocked by the Upgrades/HP/Money bar and impossibility to not take damage [or die if you're facing a swarm] once the zombies reach the wall.
Third, the little part where the world gets dark and the player uses a flashlight just amazes me. I can tell much effort was put into this game. Not many people who do a cosmetic change in their games nowadays make it have any relevance, but this one shows that the player has been guarding the wall, day and night from the incoming zombies. Although it's a small thing, I commend you for doing that.
Fourth, your game is really fun (and addictive) to play. The controls are simple and very understandable. Along with that, the zombies tend to either go one by one or in a massive swarm. Giving a good challenge to the players.
Overall, this really is a very good game. I would recommend it to anyone who looks to play a PvZ-esque shooter survival game. My only suggestions are the prices of the weapon upgrade be slightly lower once you got the SMG, because if people would spend most of their cash on barricades and turrets, then there's a very high chance they'll unlock the AK Soldier before they got an AK themselves. And NG Medals, since there is a lot of room for achievements here. Other than that, you've got an awesome game. I highly recommend this game.
