Amazing concept ! I can't wait to play the full game.
The level editor is such a great toy too. I spent all my evening making puzzles x-)
Congratulations on making this game, good luck for what's coming, and most of all : THANK YOU for this !
Hotkeys for level editor are given on the game page.
Some of them don't seem to work, I just tried every touch on my keyboard until I figured out which does what.
I think TAB opens the menu where you can choose which tool you want to use (aka: which game element you want to clone somewhere in the level).