Refreshing and interesting idea. I enjoyed playing through a few levels.

A "no tutorial" thing is probably what you're going for, and I usually appreciate that in games, but sometimes a level starts and I have no idea where to begin. But for the most part it is intuitive and the player could figure it out after a few seconds, so good job with that.

A few complaints:
There should be more simple levels after level one with the goal of mastering drawing and jumping. Level 2 doesn't let you draw boxes and that really threw me off. This is why my least favorite aspect is the learning curve.
When a level starts I have to scan and search the screen to find my box. I'm not sure how to get around this.

Are you going to implement a way to erase boxes?

Some potential bugs I found:
The green following square pushes you continuously when you are beside it. Intentional or a byproduct of it trying to get under you? A few times I was able to double jump when pushing against a wall.

Overall very fun. You are doing a lot right for sure, I'm just nitpicking.