How to get started? - Addressable Lambda Effect

Hey guys,

I have a new addressable LED Strip with the FastLED component. Everything is working fine and I can install the pre-defined effects.

Now, I want to create custom effects - but am honestly quite overwhelmed… so I’m asking for your help. The goal is obviously to understand how it works, but I just can’t get started.

The most basic effect I want is basically flash the first and last 20 LED’s in a certain color.

Does anyone know how this is done or where to learn more about this kind of stuff?

Thank you in advance!!