Well, it is playable but very much seems like a "still in development" game, good for getting practice and lots of feedback from the community.
Criticisms:
Creep spawn timer starts before giving me instructions to place turrets. Should have a “START TIMER” type button. (I only had it happen on the Tutorial Map.)
The Arrow that pops up to point to the turret buttons seemed to not line up with the buttons, it kinda pointed past them to the right side of the screen. (Tutorial Map.)
After placing more than two of a turret type, I found that after upgrading two of them, all of the other’s were showing the “Max Upgrade” text and were unable to be upgraded.
The You Won window popped up, disappeared and reappeared in an infinite loop. Clicking the Replay or Quit buttons did nothing. Creep spawn timer continued to run and creeps continued to spawn. Had to reload the page to play another level. Outside of the tutorial level, I didn’t seem to have any problems with the game over popup window’s buttons or the pause menu (didn’t check every map though).
The ESC key would pause the game and freeze the You Won window but the Replay and Quit buttons still did not seem to work.
*Not important but good for polish, consistent capitalization. “play” instead of “Play” on the starting menu and “You won” instead of “You Won” on the You won popup window.
Title says Zombocalypse but there is nothing in the game, background graphics or sprites that seems to have zombies anywhere.
Could use a “Next Wave” button to send next wave immediately.
Clicking on a turret brings up its Upgrade/ Sell menu but to make it go away I have to click on the turret again. The expected behavior is just to click anywhere else on the map and the menu auto hides after the object loses focus.
Sell price of turret says the same after upgrading, is this intentional?
No visible hit points on creeps, maybe intentional but it does seem like this type of rapid paced tower defense would have an HP bar on creeps, at least when the cursor is having over them.
When selecting a turret type, there should be something to show which turret I have selected. Either a ghost sprite follows my cursor around on the play field or the button the right side of the screen needs to look different after being selected (highlighted, change of background color, something).
Being able to move the camera around on the x,y, and z planes is neat, but seems to be a feature that isn’t needed or useful. Should also put the text boxes on a different level than the play field. If I can move around the camera, I should still be able to see the Timer, Money, and Next Wave info just like I can still see the Turret buttons no matter where I move the camera.