I'm working on a little project to create an educational device. For this, I want to be able to have a line of LEDs about 7-8cm long and be able to turn each light on and off.
But the resolution needs to be pretty fine, so they need to be tiny, and very close together.
The maximum density I've found in commercially available LED strips are 144/m which is about 1/2 what I need.
It doesn't need to be flexible or RGB, just single color.