By including `#define RGBLIGHT_LAYERS` in your `config.h` file you can enable lighting layers. These make
it easy to use your underglow LEDs as status indicators to show which keyboard layer is currently active, or the state of caps lock, all without disrupting any animations. [Here's a video](https://youtu.be/uLGE1epbmdY) showing an example of what you can do.
it easy to use your underglow LEDs as status indicators to show which keyboard layer is currently active, or the state of caps lock, all without disrupting any animations. [Here's a video](https://youtu.be/uLGE1epbmdY) showing an example of what you can do.
To define a layer, we modify `keymap.c` to list out LED ranges and the colors we want to overlay on them using an array of `rgblight_segment_t` using the `RGBLIGHT_LAYER_SEGMENTS` macro. We can define multiple layers and enable/disable them independently:
```c
// Light LEDs 6 to 9 and 12 to 15 red when caps lock is active. Hard to ignore!