The art style is great, the movement is fluid and responsive and the audio is simply superb. I really like how the atmospheric music synergizes with the color palette. Very grim looking world indeed.
I have a mixed experience with the jumping here. In Opera browser and hardware acceleration disabled I sometimes jump all the way to the ceiling (well at least 5 times as high as with a normal jump, I can skip climbing ladders this way). If I play it in Chrome with hardware acceleration enable d then sometimes the move + jump simply does not work and my character fails to jump. Perhaps this is worth looking into.
Personal remark: I really hope you will focus more on puzzles and meshing out this dark world rather than creating levels that require us to perform pixel perfect jumps :)
Really promising. 3 stars for the Alpha..obviously will rate it higher when it is finished.