Conway's Game of Life

Rules

• Cells can be dead or alive.
• Cells exist on a rectangular grid of a given height and width.
• For each cell, consider its 8 neighbours.
• A living cell stays alive if it has 2 or 3 living neighbours. Otherwise, it becomes dead.
• A dead cell becomes alive if it has exactly 3 living neighbours. Otherwise, it stays dead.
• All updates happen simultaneously.
• Cells at the edge have fewer neighbours. The missing neighbours are considered dead.
• Alternative: The grid wraps around at the edges, so it forms a torus.

Examples

Try some classic life patterns:

      .*.    ...    .*.
      .*. -> *** -> .*.
      .*.    ...    .*.

      ....    ....
      .**. -> .**.
      .**.    .**.
      ....    ....

Output

• Write a #to_s to display the grid (test driven).
• Write a runner to run and display generations on the terminal. This should be simple enough not to need tests.
  • Can you make it stop once the board stops changing
  • Can you slow it down?