This is a wonderful effect that can be used as an add on, or natural progression after doing Stratosphere. It is also a stand alone effect.
A stand is shown. Three doors can be shown empty.
Have a helper from the audience place the balls in any order they like on the stand. Then have another spectator change the balls however they want to and a third spectator can then select one of the colors.
Remember the audience that the first helper placed the balls randomly, a second helper changed the order and the third one selected the color but despite all that you knew in advance what would happen….
Open the two doors under the colors that were not selected and then last the selected color which has now the arrow pointing at the selected ball.
You can talk about the colors of the traffic light as you do this effect making it a safety lesson for the children in attendance.
Design may vary slightly