How should I structure a game engine/graphics library?

I'm writing a graphics library in TypeScript, but I don't really know how to structure it.

My file structure looks like this:

• src
  • lib.ts (Imports and exports everything from the other files)
  • game.ts (Manages and renders the game)
  • canvas.ts (Puts the image data from a Game object onto a canvas)
  • math.ts (Math definitions like Vec2, Rect, and dist())
  • util.ts (Useful functions like getting a circles bounding box)
  • sprites.ts (Sprite classes like CircleSpr and RectangleSpr)
• dst (The compiled JavaScript code with maps)
  • lib.js
  • lib.js.map
  • game.js
  • game.js.map
  • etc.

I feel like I'm doing it wrong because I of things like lib.ts where I just import everything and export it.

If anyone has made a game engine/graphics library, then please let me know how you structured it :)