Thanks for all the great feedback, it really is helpful. I've got a lot of things coming, some of which will provide more use out of walls. I've got a "container" node coming out soon. Nodes that are randomly spawned in the fog that contain...something. Sometimes good, sometimes bad. The "bad" ones will be obvious, and you will want to wall them off, to prevent balls from accidentally opening them. It's a start!
I think the amplifier just needs to be more clear too. It multiplies how much the ball takes (from a Void OR a Gold brick!). So pass through an amplifier and bounce into a gold brick, and watch how much extra you gain. Still...the point is, I need to be way clearer on that. Again, thanks for the feedback, it's helping me in this early stage of development!