Sorry to put it this way, but your coding abilities aren't that good to make a game.
Once the pipes start to show, the game gets extremely laggy and pretty much impossible.
Epic mega mega tower=1 mega tower with 4 orange area thingy, 1 mega tower with 4 sniper tower and 2 mega tower with 4 machine gun tower each.
Build it in the start of the path and your unbeatable! :D