Boulder Puzzle:

You can push stones, to the right and to the left. 
You can drop stones on the heads of the monsters. 
You can use the arrow keys for movement of your hero. 

You can suck an emerald or ground when you press the control key and an arrow key.
First press the left control key, then press  an arrow key in the direction, where you want to suck.     

In some Maps, you must lead the butterfly against a green bloc. 
With a collision against a green bloc, you will get an emerald. 
Do not forget to run into the exit if you are ready.

Peter   