First - thank you for the TypeScript support, it's a wonderful thing.
One thing I noticed, which you may be able to see replicated here:
https://codesandbox.io/s/j40262x8zy
Certain module imports show an error Cannot find module with red underline. I have created ones called model.ts, sierpinski.ts and Painter.tsx. For some reason the import of ./model in index is fine, but several others show the error.