Gimmics,artstyle and level design (mostly) is amazing, i think there is something to fix in your game. Art is amazing by itself, but I think if there were some post-processing effects in your game, it would be look a much better, but unity have a lot of them, and it`s not hard to implement into your game, so try it out About gamedesign - everything concerning core mechanics is perfect (for me atleast), that walljump saved me many times from falling. But i think it would be more interesting if bullets that we destroying was not destroyed but reflected, it would give more depth to attack mechanic. And also, my favourite mechanic one is that with spritemasking, for me it was a first platformer game that uses that mechanic fits to all game and adds depth to whole game, secrets is my favourite implementation of that. Leveldesign is too good as well for me, but i wish there would be fewer turrets in the game, but maybe if bullets was reflecting as i suggested before it could be fits for it. Well, for your first game (if it is, according to your itchio account) its REALLY good for sure, i hope i helped in your further gamedevelopment! Oh, yeah, check corgi engine, this is asset for unity for platformer games
p.s sorry for mistakes, english is not my main language