prototype of new bag

I made a sketch of this bag about a month ago while travelling to work in the tube. I wanted something round, roomy and easy to carry.
This first prototype is still missing the front pocket and I finally changed the shape of the top, making it straight. Now I know a couple of things I have to modify in the pattern and some clues about the process of sewing it.
I like experimenting with patterns, messing the whole thing up, leaving it aside for a week when it's not coming out as I want to and get back to it with a clear mind.

This was the sketch:


And the first prototype: