Press big green button to make clones. Press the blue button to magically transform the balls - all at once! Press the green check mark to make the balls bounce around. Challenge #1 : Change the check mark to an 'X' when it's clicked, so you know clicking the 'X' will stop the balls from bouncing. Challenge #2: Add another button. When the button is clicked, make the balls shrink. Or something else! Challenge #3: For the button added in #2, make clicking it "toggle" the ball size. The first click makes it shrink, the next click makes it grow, then shrink, then grow, etc.
For instructional purposes.