it works on Firefox 54, Chrome 60, IE11 (must allow ActiveX though..) and probably some versions that are a little older.
Use your mouse (perhaps it works with fingers on a tablet/phone) to scroll through the world.
There's a minimap to show you where you are.
You can also drag the minimap for fast-travel!
The green lines indicate where each door (and sometimes map edge) leads to. Arrows indicate one-way tickets.
The brown arrows are guestimated (the only ones that weren't in the Let's Play I watched).