On the Subject of CA-RPS

“Funny fish module.” -You know who you are.

On the module is an 8×6 grid. Each cell in this grid can be either Rock (Red), Paper (Green), Scissors (Blue), or empty.

The state of each cell in the initial grid is changed by number of rocks, papers, and scissors amongst its eight* neighbouring cells:

  • If the cell is empty:
    • If all neighbouring cells are empty or there is a three-way tie, the cell remains empty.
    • Otherwise if there is a two-way tie, the state of the cell is changed to the state that wins against the other.
    • Otherwise, the state of the cell is changed to the most abundant state of the neighbouring cells.
  • If the cell is not empty:
    • If the cell wins against at least as many of its neighbours than it loses against, the state of cell remains unchanged.
    • Otherwise, the state of the cell is changed to the state that wins against its current state.

*The edges of the grid wrap around to the opposite side, therefore every cell in the grid has eight neighbours.

To change the state of a cell in the grid:

  1. Press the rock, paper, or scissor button.
    Select a state that is already selected to change the selected state to empty. The empty state is selected by default.
  2. Select a cell in the grid to change its state to the one selected.
  • The clear button changes the state of all cells to empty.
  • The reset button changes the states of all cells to their original state.
  • The submit button is pressed to check the current configuration of the cells in the grid against the expected final configuration.
    The module is defused if the configurations match. Otherwise, a strike is incurred.
Cell is empty Cell is NOT empty
  • All neighbours are empty or 3-way tie: empty
  • 2-way tie: state that wins against the other (one of the adjacent ones)
  • Otherwise: Most abundant neighbour
  • If the cell wins at least as much as it loses against its neighbours: unchanged
  • Otherwise: state that wins against its current state


  • Click a square to select it, then press R/G/B/K(Space) or click the color buttons to color the selected cell.
  • Click a selected square or click outside the grid to deselect it.
  • Right-Click a square to mark it
  • Colorblind mode shows the color letters in each square.
  • Use the buttons below each grid to save the state, reset saves, reset the grid, or reset everything.