Yuki : I flew today.
Frog : Are you kidding...?
San Francisco has a lot of hills, you can play with them. Go to the top of downhill, then make sure no people around you. Then.... run and jump!
Let's say you jump A-height( what's A-height? see the illustration above ), you will feel as if you jump B-height. If you jump and run all over again, you would probably feel you are flying :D