[dahart]

The browser doesn’t communicate such things between unrelated clients, say, on different domains. The browser does allow a site to communicate with the popup that it opened, which is what this game is doing, and is not problematic.

[sdeframond]

Are you aware of the window.screenX property? It does not really seem to have any restriction. Does it?

https://developer.mozilla.org/en-US/docs/Web/API/Window/scre...

[dahart]

Yes, you can access window.screenX for your own window, but not for other windows. If you’re writing code for an iframe embedded into a domain that’s not yours, your code does not have access to the parent’s windows.screenX.