How does a selection logic for Conway's Game of Life work?
What they're doing is probably something like this:







simulate this circuit &ndash; Schematic created using CircuitLab

The current state of the game is held in U2. One at a time, 9 cells are evaluated and the new state for the center cell is generated and loaded into U1. Both registers are shifted to the right one place to evaluate the next set of cells. Note that U2 is connected to recirculate the data during this phase. After 25 clocks, the new state for the entire game is in U1, and a parallel transfer from U1 to U2 then makes this new state the current state.

The DIP switches for the initial state are probably connected to the parallel inputs of U1. The LEDs are connected to the outputs of U2, and the game is paused after every 25-clock update cycle so that you can see the results of each step. The "speed" control is really just controlling the length of the pause.