I really like those "do something hard in a short time" challenges. I join them all the time, often to fail spectacularly, but I don't mind (much). I like the rush of trying really hard with other like minded challengers, and the structure of it helps me focus and be more creative. Even if I don't make it to the finish line I've gotten farther on those fun projects than I would on my own.
This time I'm doing my own sort of challenge, one I made up for myself. I have no idea if it'll work, since I'm missing the competitive element, but it's worth a try. In the month of September I'm going to try and make a small art pack for RPG Maker. If anyone wants to join me, they're more than welcome.
