Very cool game. The difficulty curve was brutal but I would say it didn't feel really bad. I felt I was learning as the game went on. I got stuck on the level after those 3 grey balls, but even though it was impossible for me it still felt like I might be able to get it at some point (you know? it's hard to explain).
But yeah would definitely be nice to have a swinging action (like neither push or pull, just hold). It would make the game easier to play.