ah okay, maybe it got missed in the final version i shipped but go ALL the way up those stairs, and look at the big builder. You can push it. Then it will allow you to jump on top of it from the left side.
Also it looks like you missed a shortcut you can unlock. The opening of the shortcuts is the main concept of the game. One person gets far enough to open the shortcut so the next person can get further.
Try going slow and exploring between the pushing blocks room and the water room.
Also you’re not quite finished. 60% maybe lol