I've been writing my engine on and off for the best part of 20 years. It has several nice features like blended animations, flexible materials, shadows, PBR (of sorts), etc., but I don't think I'll ever have the time to finish it and when I get hooked by it, it tends to consume me completely. I've got a young son and I'm 53 and over the past few months I've been feeling a little sad that those [probably several] thousand hours of hard work are just going to sit decaying on Git forever.