I created a coaster that uses an existing interaction (putting a glass on a coaster) to close a circuit and complete the lamp. My original hope was that when different glasses/drinks were placed on the coaster, different colors and shapes of light would be illuminated– a modular lamp of sorts.
The circuit works as hoped: the lights shine when (and only when) a glass is on the coaster. But if I were to do it again, I’d use brighter lights and/or a more transparent surface for the lights to shine through. As is, it’s a little dim.
Instructables link: https://www.instructables.com/id/LED-Coaster