That's actually a hard question as I enjoyed what I played and just want to say "more of the same". I enjoy the confined spaces and instant readability of the game so would be afraid of adding too much - although one thing I've recently started apprecating much more is speed running - a "ghost" mode of other players runs could be an interesting addition because it would make me interested in seeing the same levels over again and trying alternative solutions to some of the levels (or at least laughing at how bad I was!).