I'm not entirely sure, but there seems to be a memory leak in the game. When I let it run for about 3 hours in a row the game got really slow and eventually stopped completely. It gave me an error about allocating more memory to OpenGL and that it had run out of memory.
I had a small issue with the level not ending after i apparently killed all of the enemies. I even waited quite a long time to make sure they weren't pushed back or anything. I didn't know how to manually exit, so I just refreshed the page.
 "The Perfect Tower"){kind=icon}
 "Base Defence"){kind=icon}
"Esc" :)