A large part of Celeste is its mood and atmosphere. We’re trying very hard to make it feel like you’re exploring (and overcoming) a Mountain, and so lighting plays an important role.
We decided early on the lighting had to interact with the environment. As the game is about maneuvering and climbing through difficult terrain, having simple “Spotlights” wouldn’t cut it — the lights needed to actually hit walls.
Left: Lights that collide with the terrain, Right: “Spotlights” that have no ineraction
MESH IMPLEMENTATION
My first implementation of the lighting was fairly complicated. I wanted something that would be fast and allow us to have lots of lights, so I decided the best way to do this would be to construct a Mesh for each light, and draw them all at once.