Selden: There is a tragic flaw that people considering buying the game should be aware of.
AI has no way to subjectively judge the worth of art. There are a few things it looks at, like minimalists dislike having a bunch of different colors while the aristocracy likes the slow brush tool being used, but by and large there is one thing that determines the value of your artwork: time spent. If you take half an hour to draw what looks like it should go on a refrigerator, then so long as you aren't doing something to tick your specific customers in later chapters off, it will sell for more than your friend's who spent ten minutes to put together something that may actually be art when viewed from the correct angle.
Aside from that time = money issue, it's not a bad game for playing at being an artist. You can't erase - you're a painter, after all, not a digital artist! - but you can paint over mistakes and try again. The color palette is a bit limited, and you only have three tools to use; a paintbrush, a brush that follows where you move the cursor but slowly so it won't be exact, and spray paint. If you enjoy doodling in Passpartout, perhaps you can move on to a more expensive digital art program.
That's interesting. I have a friend who recommended this game to me, but warned me of a flaw he finds irritating. Across the whole game, he'd put enormous time and effort into a painting, only to find that no-effort paintings he turned out in a few minutes sold better and pleased the critics more. Exactly the opposite of your experience. Perhaps his taste in art conflicted with his customers.
He was wondering if the game did it deliberately to increase the simulation of being an unappreciated artist. ^_^ He had a lot of fun with the game regardless.