For years I've been fascinated by those little solar-powered calculators. In a weird way, they're devices that enable us to cast hand shadows to do arithmetic.
Lookup "Analog Optical Computing". There was recently a breakthrough just last week where optical computing researchers were able to use photon interference effects to do mathematical operations purely in analog! That means no 0s and 1s, just pure optics. Paste all that into Gemini to learn more.