You can actually play any WIP offline.All you have to do is, open all available scenes on the game you are playing.This is not useful to the games that does not allow you to revisit a certain scene.
Because once you open all scenes, you won’t need internet to load the scenes anymore.This will continue to work until you have closed your browser.
I stand to correct myself.Even if you leave your browser, you can still come back and play it offline.Though you will need internet to refresh the tab with that WIP.Also accessing your saved games will still need internet.
I find this helpful considering I have a WIP that visit the same scene regularly.Hope you find this helpful too.!