I found that the materia and money system only really played a part right at the beginning and right at the end. Perhaps make things a bit more expensive so you have to pay attention to them throughout the whole game.
I think it was Antimony (the one with the zig-zags on top) that needs a few extra circles or you can just draw a line straight across, and the curved bottom can be a triangle.
I did like seeing the money go up at the end, although I did almost miss it. Perhaps instead of having it overflow and go negative, use the infinity symbol?
Overall, not bad! I finished it in 16:53