[I played the current web version]
I really enjoyed this! Haven't played around with the editor yet, just the 9 main levels, but the mechanics were well-taught, levels naturally explaining the power of your movement, and the style was great. The music and textures fit together really nicely.
There's only two things I might change. The first is the background; most of your level geometry is a dark grey, and a dark grey or black background under that isn't great on the eyes. The second is the 'Boost' block, maybe renaming to 'Push' would work better. Might just have been me, but my first instinct was that it would act like a speed boost in a racing game if I placed the active cube on top of it.