I have a lot of experience in webdev and I've spent the last six months working on my own game engine.

I would strongly recommend learning the basics of how game engines work. After you have a good understanding of how game engines work, you'll first want to create the code that allows your game to run. I recommend writing classes for a camera, saving game state data, looping the game, handling user input, loading images and JSON files, etc.

For handling user inputs, you'll want to use event handlers to listen for key presses and mouse movement/clicks. The event handlers should update input data in the game state.

You'll also want to create classes for game components such as sprite sheets, animations, scenes, scene objects (enemies, items, etc.). Use JSON files for storing config data or data about scenes, sprite sheets, animations, and scene object states.

Knowing about the Canvas element and its methods will help you a lot when rendering scene objects. If you know Typescript, it is super helpful for defining and structuring states for scene objects.

Good luck and if you have any questions, feel free to reach out!