Well, here’s the place to start…
My thought is that you could use a sensor that can measure distance and feed this value to ST. One limiting factor is how quickly the data can fed to ST and then relayed to a light to adjust brightness, especially since all of this has to be processed in the ST Cloud via an internet connection.
Have you considered just using an Arduino or NodeMCU board to do everything? There are plenty of online resources that can help get you started with learning about Arduino programming, as well as the plethora of devices that can be connected to an inexpensive MCU board. The advantage of going this route is amazing performance. The challenge will be in the choice of lighting. Inexpensive LED strips may be your best option.
Here’s an example where someone used music to alter the lighting. Just an idea of what is possible…
Here’s another example showing distance based dimming.
