The simple answer is that these days I go where the muse takes me. I'm basically on a year-long sabbatical after leaving Google this summer, where I'm not particularly worrying about making money. I did my PhD on tools for interactive curve design, and I was frustrated while I was at Google because IP issues made working on curves complicated. So when I had some new ideas, it was like the dam bursting, and I've been enjoying lots of motivation and creativity. I started the codebase for kurbo on Christmas and wrote 1300 lines of code that day. I'll keep doing it while it's fun.