A very cool thing to try when lucid dreaming is switching up gravity. I did this recently and it was awesome! All I had to do was think, "gravity will now pull up instead of down" and the next thing I knew, I had to hold onto the grass to stay down! Oddly, nothing else started flying up, just myself. It didn't turn into some lucid nightmare, either. When I was tired of holding on, I simply thought of everything back to normal and it was. What a thrilling experience!