I had fun with this, it has nice polish, very clean design. The trail behind the player adds some nice juice to the game. I wonder if there is even some way it could become functional (e.g. dragging blocks in with your tail if you just miss them, similar to how a jellyfish works.)
On the controls, I always struggle with virtual buttons on touch screens (including in my own demo). In this case, it might be a good candidate for an alternative form of input. Perhaps tilt or right swipe / left swipe, try it out?
The Leaderboard / Gamecenter integration was good, it definitely encourages me to play more to climb the leaderboard. What plugin, etc. did you use in Construct 2 to do the leaderboard integration?