Up to no Goo'd

Prototype for a puzzle game. 
Click and drag on the green goo ball to slingshot him in the opposite direction.
You stick to the walls, and you loose some mass with every movement.
You can pick up extra goo along the way to regain some mass.
Guards will pop you if you're facing them, but you can hit them in the back to kill them.

Looking for some general feedback and ideas for improvements :)