Build your circuit: Power - Sound Trigger - Buzzer - Lightwire. Secure the circuit to the top of an upside down cardboard box. Drape the lightwire around the box.
On the same box, use blocks or littleBits markers to make a pyramid.
Take a pom pom and add googly eyes - these are your targets! Place them at the top of the pyramid.
Take another cardboard box and turn it upside down. Take two Popsicle sticks and make a V shape. Secure the shape to the box.
Secure elastic to the Popsicle Sticks, creating a sling shot.
Slice a Styrofoam ball down the center and scoop it out. Place a bell, coins, or another type of weighted material in the center and secure with tape.
Finally, use the slingshot to shoot the ball at the pyramid. The sound of them crashing down will cause the buzzer and light wire to go off, so you know when you've won!