Behind each door lies a different experiment that can be easily conducted using the components and the manual, even without prior knowledge. The focus is on transistors, light-emitting diodes, a light sensor, and a small speaker. This leads to secret light signals, stored energy, light flashes without a battery, LED blinkers, and much more. Included is a detailed manual that explains all the experiments step by step with many illustrations. It not only explains the individual experiments but also provides a clear insight into how the components work and interact. The playful approach encourages creative engagement with technical questions.