Thx for explanations R0J0hound !
Now i explore others options of your cool behavior and i have a little problem with the function "position shadow object".
My idea is to position a shadow below all my blocks of sprite to simulate shadow caster so i try to do :
system - for each Blocksprite system - create object Shadow
Blocksprite - position object Shadow as shadow
But the system create infinite Shadow ^^
Ty for help me