This was great. Thanks for stealing those hours from me :P
I think I've got a bug report for you though: It's possible to complete the left-hand side without getting the item in that section. Which confused me pretty thoroughly when trying to get through the room with the three switches. The issue is that it's possible 1) to push things by using inside corners to get an angle on them and 2) to stand on the edges of tiles that are occupied by pushable objects. I used 2 to get through the item-gating room (by getting on the bottom edge of the floating platform and pushing the block up) and I used both to get through the puzzle just afterwards (the last boulder-push required jumping over the gap and *into* the boulder making sure to push it before I could fall)