A gesture sensor, from Adafruit.
It was a shame: you really like capacitive sensors; you had spent a few Tuesday nights at Cambridge Hackspace debugging a few of them so you could use them as a gateway interaction: "Just "Touch X" to..." (initiate an action).
Simple enough, right?
Now, inviting people to "touch the oak leaf" suddenly seemed like a dangerous request.
But this was not their time -- especially early in the Coronavirus pandemic, when touching was considered a major infection vector. That faded a little after a few months, in favor of breathing in airborne molecules, but it never went completely away.
Now, inviting people to "touch the oak leaf" suddenly seems like a dangerous request.
So you start converting everything to "touchless."
Your first enabler: the APDS gesture sensor.
Your three primary suppliers of APDS9960 chips are: Adafruit, Sparkfun, and DFRobot.
And then there's a fourth: AliExpress, which is a wild west of commodity chips, with a dramatic price break, and a hugely long delivery period -- 30 days plus.
You had already gotten one big project going with a Photon and the Adafruit APDS9960: the Gumball/Gachapon machines at Fab@CIC and District Hall. Both were working great, when the Coronavirus hit.
With one little design flaw: You originally created a little box with some available pink acrylic sheets, with an opening to expose the gesture sensor. Fine. The instructions say, "Wave your hand over the pink box."
But people don't read the instructions. Many of them just put their fingers into the box and press down. Of course that works -- it's a pretty serious gesture -- but it's not ideal.
You try to cover the opening with something transparent. Doesn't work.
So you have to get back to that.
You had also gotten going on an Arduino + APDS9960 combo. But the Coronavirus cut that project short: the Tuesday night open project nights, where/when you worked on it, evaporated when Cambridge Hackspace closed. And you were close.
But in the meantime, this was an opportunity to expand your explorations of this chip.
Fortunately, Adafruit, Sparkfun, and DFRobot all have extensive documentation.
They also have libraries on Particle and Arduino platforms. And examples. Plenty to work with.
Here's an awesome gesture sensor, available at Adafruit.