A sandbox you can play with, and a plain walkthrough of what it shows.

No mind sees all of reality. Your eyes take in a sliver of the light in a room, your brain throws most of it away, and what is left is a compressed, useful sketch you act on. Any observer that is part of the world, whether a cell, a brain, a computer, or an AI, faces the same problem: there is far more going on than it can track, so it must compress.

This page lets you measure that. It builds a tiny, fully known toy world, drops a deliberately limited observer inside it, and asks three questions: how much can the observer predict, does changing its viewpoint change what is knowable, and if you run it forward where does the arrow of time come from? The surprise is that the answers are not about the world alone. They are about the fit between the world and the observer looking at it. Run the experiment below...