Hell yeah! I'm glad to see your prototype from back in the day made into a full game (demo)!
For me jumping feels very inconsistent. Sometimes you can jump, sometimes you can't. I understand, that jump force is controlled by the time the LMB is pressed, but somehow it doesn't feels quite right. The whole character controlls feels sluggush (or blobbish, haha) and it just becomes really frustrating.
I couldn't pass the red button that opens horizontal platform that needs to wall jump through. I spend like 10 minutes trying. And the closest I got to passing through - when the platform squishedf me without any means to get out :)
Also the jumping platform sound is really loud.
Anyway, look forward to the updates!