A version of John Conway’s “Game of Life” cellular automaton on your wrist. Living cells are colored from blue (too few to survive) through the rainbow to red then purple as their number of neighbours increases in the battle for life.
From the Wikipedia Entry:
The universe of the Game of Life is an infinite two-dimensional orthogonal grid of square cells, each of which is in one of two possible states, alive or dead. Every cell interacts with its eight neighbours, which are the cells that are horizontally, vertically, or diagonally adjacent. At each step in time, the following transitions occur:
Any live cell with fewer than two live neighbours dies, as if caused by under-population.
Any live cell with two or three live neighbours lives on to the next generation.
Any live cell with more than three live neighbours dies, as if by overcrowding.
Any dead cell with exactly three live neighbours becomes a live cell, as if by reproduction.
From these simple rules a seemingly infinite array of variations result.