OK, quite well polished game, but too fast paced for me, and: I don't have a controller currently and all that with the left hand (A,D, SPACE, A, SPACE, D, SHIFT to jump, turn right and dash right) is just impossible for me. It's not your (game's) fault, I'm just not intro this fast paced platformer die everywhere genre.
That is also the reason why I cannot really give good feedback here :-( because "I know shit" and I would recommend to be more forgiving, reduce movement speed, make different = more interesting than hard levels, etc etc... all these statements that quite surely make no sense for you and your aimed at players.
The RMB shooting is interesting but really hard for me to use, too. However:
Here is maybe the only useful No.1-recommendation (but only for keyboard players): RMB is the only thing that I can and (unfortunately) _have_ to do with my right hand (mouse hand). This hinders me to use my right hand for the CURSOR instead of WASD - that _might_ help me just a ...tiny bit... to use right hand for CURSOR and left hand for dash, stump, jump. That said... well... it does not work easily, because it's not just the RMB but also the mouse direction that's needed from the right hand. Soooo... if you would want to think about some crazy alternative to RMB(+mouse) you would have to think about a pointing aid for the shoot direction. Meaning: either the shoot dir is always full automatic or you would have to use some (last) cursor movement for a rough dir and fix the rough dir to the "correct" one... Bla bla bla... this is 1) complicated and 2) probably not dependable a control and 3) only for weird noobs that better should "get better";-) ... which I don't :-P
Reco No.2 is: think about taking the time to do a gameplay video. Reason is: players should also see later parts of the game if they are even cooler than the first levels. Just thinking.
Ah yeah, and for the web version for this fast-pace game requiring SPACE and RMB it is essential that you change the display settings to FULLSCREEN, it's really a must.
The gfx and music is fine and make this "for-me-horror" trip actually still a pleasant, enjoyable, funny time.
Sorry if the feedback is not that useful for you, I am the wrong player for your type of game. Keep up the mood and dash further!