The city environment has been started. This is still heavily a work in progress. Here is how it works for now:
At wave 30, enemies stop spawning, and the player's vehicle spawns to evacuate the player to a new area. When you reach the new area, difficulty is increased, and the enemy wave counter is reset.
Reaching wave 60, (and 90, 120, etc) will transport you to the next environment. (for now it just loops the 2 available ones)
In this update:
+2nd environment started
+evac truck
+made player and items persistant
+game controller persistant
+achievement for 50 exp levels
Planned future updates:
-New enemy types for level 2.
-New mini boss types
-Main boss at the end of each environment