I recently discovered that near the end of last year Amazon released an update (v5.16.4) on its e-readers (Kindle, Paperwhite, Oasis, Scribe) and they completely revamped the built-in web browser. I know, it sounds incredible, but now it works quite well.
The most pleasant surprise was that I was able to login into my CoG account on their website and now I can play my library on my e-reader web browser! It’s simply beautiful to read these games on e-ink. I have played three titles (400k+ words) so far, and everyhting worked perfectly.
However, I believe there are a couple of caveats: first, the web browser warns you that it is simple and that it doesn’t have much cache. Since, as far as I know, the games you play while on a browser store their progression in the cache, I think you should clear it every two-three games you play, so you won’t lose any progress (you’ll have to login to CoG website again though, but if you save it among your bookmarks that’s no issue and it’s fast). I’ve seen that a game stores about 9 MB of cache, so not much (please correct me if I’m wrong).
Second, I read simultaneously both a normal ebook and a CoG game, but I never turned off the wifi or navigated the web. I only opened the browser to play my game and then closed the browser before locking my e-reader, every single time.
Now, I think it should be useful to try all possible kindle-based scenarios and to check if some of them cause progress lost (I still had not try to turn on/off wifi between sessions, to lock the kindle without exiting the browser, to surf other pages and return to the CoG website later, and so on and so forth).
Finally, I suggest to switch to the white background from the default sepia one, so that you have an homogenous color (the kindle’s one). It’s prettier this way!
Let me know if it works well for you too, and if you encountered any issues, so that we know what we should and shouldn’t do with our kindle’s web browser!