You can try a first build of the game here :
Beware, it’s extremely buggy, and mostly unfinished. There is no text display (that could explain what to do in the first level (go back to the buildings when you’ve been to the lake))
There is only the first 4 levels, more demonstrating the different gameplay element than a real level design exercise.
The first level introduce the doors and the collectables.
The second level introduce the activable elements.
The third level introduce the jump boosts.
And the last the attractors.
Every thing here is only a work in progress so be patient and comprehensive.