That would be the ~ (tlide) button. It opens Ned (N level EDitor) and I think I made up to 50 levels in two months. But then that computer broke down for good. N doesn't work on Windows 7, to my knowledge.
The chaingun drone is evil.
But fun. Useful for testing reflexes
I hate those Missile Turrets.The Defender
(I think there are two such games, I'm only aware of one but different one is mentioned in the Cheatbook Database program) is neat.
Some hooded guy fights an army of ghosts. With the gold, one can build a tower, hire archers, cannon-guys and wizards, and with the ghost essence unlock neat things like 2-player mode.
I remember something of "venusgames.tk" but I am not certain.