I suck at platformers, but I can appreciate how well designed this is. The hanging from ledges, sliding under obstacles, color-key doors - it's really nicely done. And the artwork is great too!
I am a numpty, and reading in-game text isn't really my thing. I could've done with an extra something (SFX, anim, particles?) to tell me I'd picked up a keycard as opposed to some other generic pickup. Or maybe a really obvious 'need red keycard' when I face-butted the locked door the first time?
Anyway, it's fantastic work! Nice one!