The yo-yo world !

There are two types of yo-yo:

• Responsive yo-yos: these are the yo-yos of our childhood, those that go up the string as soon as we give it a little tilt. They are used by beginners.
• Irresponsive yo-yos: they don't come back up ! It will be necessary to make a "bind" to make it go up the string. (trick which consists in doubling the string so that it grips and makes the yo-yo go up).