Going back to our newer game, I realized that I am supposed to figure out where the number given should fall on the line.
A case study in modern useability - looks a lot cooler, can't figure it out.
Also, both of these tickled my brain in a great way. I think a potentially fun continuation would be to "eyeball" physics. For example, throw a ball and pause the physics before it hits something (ground, object, who knows?) and guess the location. Or show two objects about to collide with certain shapes and masses and guess what one of them will hit first and where.