In 2004 I played too much RuneScape on a 56k modem that died the moment Mum picked up the phone. A 3D world, up to a couple of thousand players on a server, dozens on screen at once - in the browser, on 5 kilobytes per second. It worked. Let’s follow a single step and see how.As a child I was too preoccupied with picking flax and killing goblins to think about how this worked. The answer, however, is a sustained, almost obsessive exercise in not wasting bytes. So, let’s click one tile north of w...