Implement one or two interesting post-processing effects. They can be any effects, not just the ones described in the material. You can also come up with your own custom effects to serve some specific purpose, as long as you are able to explain what that purpose is and how you achieved it. The effect has to be a post-processing effect, meaning that it needs to run in a separate rendering pass. The solution is not to just use a pre-made effect asset, but you need to implement the effect yourself. However, you can use online sources as long as you cite them.

Here is an example from Blastronaut, where the entire screen gets greener when the player character is inside a poisonous area:

Blastronaut

Your effect(s) need to be optimized enough so that the framerate drop would not be noticeable.

Be creative!