While waiting for research to finish, I looked through the sprite atlas (F3) and found these glowing heat pipes:
![Image](https://forums.factorio.com/images/ext/31781560070d795b4df90085c27efc07.png)
While building my first reactor setup, I was kind of disappointed that the heat pipes didn't glow and now I found these already existing sprites.
Does anyone know why those aren't actually in the game?