A turtle will move more slowly if you decrease the distance it travels repeatedly. A turtle can be set to move forward by a fractional or decimal amount. On fast computers, we often need to slow a turtle's speed with division, sometimes in combination with a slider.

to fly forever [fd speed / 100] end

Method 2:   Use wait. See Animate Me 4.

A turtle will move more slowly if you increase the amount of time it waits before moving again. If we write wait speed, then a higher number makes the turtle move more slowly. We can use subtraction so that a higher number makes the turtle move more quickly.

to bounce forever [fd 100 wait 10 - speed          bk 100 wait 10 - speed] end Try moving the slider while the ball bounces. Which setting do you like best?