Public Code Review

Learning is much easier for me when it's relevant to something that I've been working on. In the spirit of learning in public, I want to crowdsource some knowledge on what can be done better in my DigitalOcean project.
Here's the project submission: Tic Tac Toe Arena

The project is functionally complete, and I'm pretty happy with how it has turned out, but there are definitely some decisions I made that might not be the best.

I've created a few issues (and will probably create more later) on some code that I feel like I need guidance on:

1. Rerendering with a model-based approach
2. Evaluate custom code

There are probably other issues lurking in there as well that you feel you can teach me about. If so, feel free to comment below or create an issue in the repo.