I'm not sure if it's the settings for the graphics here, but, the textures seem a little on the low res end of things. If this is intended, I would find a way to play with scale a little bit.
I really enjoy the world building here, but, one major area of issue I am having is navigating. At the beginning it is made quite clear how I progress, you give me just enough information to move forward. Once I clear the ball I am excited/overwhelmed within the first few seconds of moving. The invisible barrier is actually a bummer to find so often, part of this is, the path is unclear, so I just run into it quite a bit. A solution is using props/color to guide our eye. Similar textured props with colorful elements can be grouped to create a visual map.
Now for addressing the question of puzzles. Try to create a simple map of your level top down, and, address your puzzle making in phases of difficulty.
1st phase - easy - push block, climb over, push ball remove barrier
2nd phase - medium level of difficulty - do we push and STACK things? This would challenge how we climb and find our pushable items and how we line up the drop to stack.
3rd Phase - limited items pushed into place and timed jumping.
These are just some possible physics based mechanics that are simple yet effective.
Great work thus far!