Free rein is always the most enjoyable, I agree, though having boundaries to work within can be a welcome challenge every now and then.

Actually, I'm rather jealous. I'm a lost cause when it comes to most forms of math--it just doesn't compute the way grammar and writing and words always have. I did enjoy equations, but if they didn't work out, I got terribly frustrated with them, so they were still more of a chore than a means of relaxation.