This is actually one of my favorite reasons to go for a hike! I can put a little music on to keep my mind occupied (but not always; nature is nice) and then, since I really can't read or be distracted, my mind is happy to wander. I must look like a complete fool, having spoken conversations with seemingly no one, as I talk through whatever comes to mind and turn it over from every angle. I've designed several systems in my game engine this way, almost entirely on accident. It's like my brain just needs permission to do its own thing for a while.