I like the idea of the game, it has potential.
Sadly I got really frustrated by the controls. Generally the double jump, split and cube/anvil transformation buttons sometimes work, but mostly dont or only while hammering them. It feels like you are only processing one button press at a time (no jumping or splitting while moving etc). Additionally all the controls are pretty awkward to keep your hands on at the same time (tab, space and control)
Make sure that you check all buttons down in the runs of the update/fixed update functions and if you have problems with the same button press triggering in multiple runs of the update function try using Input.GetButtonDown since that only returns true in the frame that the button was pressed.
I also got weirdly stuck in walls and jumping felt very floaty. Still I like the general concept.