ZPD: zombie police department

I like the theme and how it currently looks. It's a great start for it to turn into something great, and excited to see the development progress. 

General Feedback:

• Unless you can get more than 3 upgrades each level, I think the upgrades are spaced too far apart
• Tree collisions are too big
• Does the fire rate upgrade work? I had upgraded it a few times, and didn't feel like there was a change 
• It would be nice if there was a confirmation to restart the level
  • I didn't press the 'R' key accidentally during gameplay, but would be a nice safety net
• You can see where the grass is being tiled, would be good to have this be seamless 
• The map feels a little empty with the number of enemies spawning

Bugs:

• You can reach the edge of the map and fall off
• Level and experience text overlaps each other, and goes to a new line
• You can stand inside buildings, bushes, trees etc
  • Sometimes you can get on top of the bushes
  • For the trees, you can push yourself inside of it and fall through the map
    
  • In some cases, the zombies and bats can't hit you when you are inside one of these objects 
  • Since the XP goes straight to you, I could stay in one of these objects to gain some free XP until I started to get hit, or one of the flaming skulls was approaching