The Solarengine circuit in the Solarbotics Solar Marble Machine stores the light from the solar cell, and releases it in an occasional pulse that drives the mechanics. In sunlight, the motor will pulse every few seconds, and drop a ball every half minute. In indoor light, motor pulses decrease to every few minutes (be patient). But you can always use the hand crank to manually advance the marble wheel. This kit requires basic soldering tools (soldering iron, solder), a Phillips #1 screwdriver, and a small amount of white glue.