pressure sensor and they fit together magnetically and create circuits. you can so how easy it is to turn in and turn on the power here. this is a power and dimmer and i can turn the light up and off and on. can you pick andment. they fit together a concern way. and it comes with a great instruction guide. parents can get involved as well. tell me the age? eight and up. it is a hundred bucks but for all of the ingenui ty it is worth it. what is that this. this is the twilight turtle. it is hard to see.