Thank you very much :) at the moment I don't have much time.  I have ideas in mind but I'm waiting for version 3 of gb studio to play with parallax ... thank you again for your feedback

Thanks a lot !  It was easy but very long to  set up. 

You need, a big background 

See pictures below : every part of the background is divided in triggers.

At the beginning you insert your 9 blocks actors in the scene (limit is 10 but 1 is the reward, so you can use only 9 for the blocks).

Each time the player is in a specific place, he will activate a trigger and will thus move blocks (not all, only half the blocks, for example actors 5-6-7-8 in the top-center in pink ). In some place, a block is a simple image drawn in the background with a collision on it.

I hope that can help you (and others) to make great games !