Imagine a universe of only two dimensions (like a sheet of paper) inhabited by flat beings. These beings know up, down, left, and right, but the concept of "upwards" (towards us in 3D) is completely incomprehensible to them.

If a three-dimensional object, like an apple, were to cross their paper world, the flat beings would not see the whole apple. They would only see cross-sections: a point that turns into a small circle, then a larger one, and finally disappears when the apple finishes crossing. Their 2D brains can only perceive "slices" of 3D reality.

If an object with four spatial dimensions were to enter our world, we would only see three-dimensional "slices" of it.

Conway's Game of Life, the most famous cellular automaton: a grid of cells that are either alive or dead, evolving in discrete generations with no player, no randomness and no memory. Each cell looks only at its eight neighbors and follows four rules:

1. Underpopulation: a live cell with fewer than two live neighbors dies.
2. Survival: a live cell with two or three live neighbors stays alive.
3. Overpopulation: a live cell with more than three live neighbors dies.
4. Birth: a dead cell with exactly three live neighbors comes to life.

That's it. Every generation is computed from the previous one, all cells at once, and from those four lines emerge gliders, oscillators, still lifes and patterns that can run forever. The system is even Turing complete.

You can tap the screen to inject chaos: a burst of random live cells dropped into the grid. Watch how the rules digest the noise and order emerges again, pulsed by the kick.