Not bad but bug
I went to 'restart' game, and I think my towers were still at the beginning of the maze, even though you couldn't see them. And they seemed to be a lot stronger because I didn't build air towers, so I restarted at first air level, and guys died all the way till the last level at the beginning of the maze. ie I had like 3 basic towers and they were killing everything in seconds... unless the bug was just killing enemies and my previous towers had no effect, and just coincidence I placed them at the beginnning as well.