I know nothing but my recommendation if your motivation is making games: check Game Jams. They tend to have clever people coming with fun ideas and developing them in a short time, so IMO it's a great way of learning the trade.

As an example, check https://itch.io/jams and filter by "participants" and "featured" to get more mainstream, less adventurous ideas.

Some game jams that include source code: https://www.brutalhack.com/blog/open-sourcing-9-game-jam-projects/

Finally, I see casual* game development in two different ways:

I want to create games so I can become a better developer.
I want to become a better developer so I can create games.

If you're on the second case, I'll recommend getting into Godot or Unity, as they take away a lot of the hard parts in game development while sacrificing some flexibility. There are plenty of options out there beyond these two, but they tend to be the most popular ones for casual* game development.

*Anything beyond casual is beyond anything I know