This one might be for Ashley,
I wish to have a platform that is 3072 pixels wide <---------->
Window size 640 x 480.
Is this too large for a Browser, as it seems that scrolling by length is ok, but not by width.
There shouldn't be anything preventing you from having a platform that wide.
You should just be able to set it up so that the player character or whatever scrolls through the world, thus being able to see more of the platform.
You can also change the window size to whatever dimensions you want.
Develop games in your browser. Powerful, performant & highly capable.
It should be fine. One way to test it is run it and see! :)
Have tested, and it works fine, no problems