There are two bugs that need to be fixed. First mission 11 "Island" has you able to build on the spawn points of the zombies, thus making every enemy except for flying ones useless. Second mission 12 "Finale" spawns me on the blue power marker thing's ledge, unable to move. This didn't change after restarting the level multiple times and it made the level impossible due to invisible monsters being able to steal the cores without being able to stop them. The first should kind of be fixed due to how trivial it makes that level, the second should definitely be fixed.
Other than the flaw of being unable to actually complete the game, it was fun.