Dave posts his Miata modifications on Plastibots:

It’s only been a few weeks since I’ve had my new 2021 Mazda Miata MX-5. Already added sequential LED turn signals & side markers all around, but not being the type to leave well enough alone, I needed a little spice to make it my own. Combining that with my passion of microcontrollers and LEDs and taking inspiration from others before me, here’s what I ended up with.

The heart is an Arduino Nano microcontroller with an Adafruit NeoPixel RGB LED light strip. The controller takes 12V power from the rear parking light, GND and 12V signal from the brake lights (when applied). When the car starts, parking gets power which fires up the controller/LEDs with a “bouncy” LED sequence intro on car start. For the rest of the time, the lights remain on as running lights while the controller monitors the brake signal. When brakes are applied, the LEDs sweep outwards in brake mode. The controller has a mode button so I can turn features (the “bouncy” bit) on/off (see future thoughts further down).

As this is a NeoPixel RGB LED colour strip each LED (90) can be individually controlled with millions of colours (and brightness control). In this case, I’m only using red and varying brightness. The entire system can all be tweaked via code using the Arduino Nano. This way I can change it up later if I get bored or get new ideas.

See the video below and more in the article here.