First thing first, visually awesome looking game the theme is very consistent in all of the levels, like the color and the 2D art as well.
Secondly the selection of music is so well done, it fits the levels very well.
Finally talking about the levels my absolute favorite is "Walking on Eggshell"(even though you made the last stage of this level very easy and predictable). And the level which took the most time to complete was "Shell shocked". All the other levels I was able to nail down in one to two runs.
Great work. $ ship it $.