Nice concept and I like the style.
I feel the controls could be optimised slightly. It's a little cumbersome when if say I want to make a cube go right then down, I have to drag on the right module, then drag the right module back off onto me, then drag the down module onto it, then drag the down module back onto me. Perhaps if the puzzles were more challenging it wouldn't be as noticeable, but I'm not sure why I can't just drag one module on top of a cube and have the current one it's holding return to me, rather than be sprung out to a random nearby location; as far as I can tell there was never a situation where being able to simply drag the new one on and get the old one back would break anything.