Favorite topic in advanced math?

Building 4D Polytopes With WebGL

https://syntopia.github.io/Polytopia/polytopes.html

Personally, I like computational probability. Theoretically I believe it falls under the more formal rubric of "measure theory". With stochastic processes remaining a very active field. Particularly around nascent quantum computing algorithms, quantum walks, etc.

Probabilistic Models of Cognition

https://probmods.org/