Hi nice concept for game! It's got cool level designs that actually make you think!
Some suggestions; I think it's a bit awkward not being able to jump with the red block when the blue block is on top, as that would make a really cool method of getting your blue block up to heights but I understand would require a rework of the earlier levels!
I think selecting which block you want to move should be by clicking/touching the actual blocks, it just makes the game play a lot more intuitive for players
Bonus points for creating your own graphics! I love that the blocks eyes/mouths are animated, that little extra attention to detail is what really sets developers apart regardless of their level of experience