1. Find a tennis racket / book and a ball. This could be a tennis ball, a rolled up piece of paper or anything that will bounce off the wall.
2. Take 1 stride away from the wall.
3. How many times can you hit the ball against the wall in 30 seconds?
4. If the ball falls to the floor, start counting again from 0.
5. Get someone else to time for you so you can concentrate!
6. Submit your score as a whole number, for example 10