[lachenmayer]

The Graphical Linear Algebra[0] series is a fantastic introduction to a really fascinating application of category theory, representing vectors & matrices as flow diagrams (ie. monoidal categories) and deriving useful properties from those.

The style is super friendly and builds up intuition slowly, while being completely rigorous. For a great example, check out the "Crema di Mascarpone"[1] chapter which introduces all the tools for writing rigorous mathematical proofs using flow diagrams.

[0]: https://graphicallinearalgebra.net/

[1]: https://graphicallinearalgebra.net/2015/05/06/crema-di-masca...