## Full example

    // Processing implementation of Game of Life by Joan Soler-Adillon
    // from https://processing.org/examples/gameoflife.html

    // Size of cells
    int cellSize = 5;

    // How likely for a cell to be alive at start (in percentage)
    float probabilityOfAliveAtStart = 15;

    // Variables for timer
    int interval = 100;
    int lastRecordedTime = 0;

    // Colors for active/inactive cells
    color alive = color(0, 200, 0);
    color dead = color(0);

    // Array of cells
    int[][] cells;
    // Buffer to record the state of the cells and use this while changing the others in the interations
    int[][] cellsBuffer;

    // Pause
    boolean pause = false;

    void setup() {
      size (640, 360);

      // Instantiate arrays
      cells = new int[width/cellSize][height/cellSize];
      cellsBuffer = new int[width/cellSize][height/cellSize];

      // This stroke will draw the background grid
      stroke(48);

      noSmooth();

      // Initialization of cells
      for (int x=0; x<width/cellSize; x++) {
        for (int y=0; y<height/cellSize; y++) {
          float state = random (100);
          if (state > probabilityOfAliveAtStart) {
            state = 0;
          }
          else {
            state = 1;
          }
          cells[x][y] = int(state); // Save state of each cell
        }
      }
      background(0); // Fill in black in case cells don't cover all the windows
    }

    void draw() {

      //Draw grid
      for (int x=0; x<width/cellSize; x++) {
        for (int y=0; y<height/cellSize; y++) {
          if (cells[x][y]==1) {
            fill(alive); // If alive
          }
          else {
            fill(dead); // If dead
          }
          rect (x*cellSize, y*cellSize, cellSize, cellSize);
        }
      }
      // Iterate if timer ticks
      if (millis()-lastRecordedTime>interval) {
        if (!pause) {
          iteration();
          lastRecordedTime = millis();
        }
      }

      // Create  new cells manually on pause
      if (pause && mousePressed) {
        // Map and avoid out of bound errors
        int xCellOver = int(map(mouseX, 0, width, 0, width/cellSize));
        xCellOver = constrain(xCellOver, 0, width/cellSize-1);
        int yCellOver = int(map(mouseY, 0, height, 0, height/cellSize));
        yCellOver = constrain(yCellOver, 0, height/cellSize-1);

        // Check against cells in buffer
        if (cellsBuffer[xCellOver][yCellOver]==1) { // Cell is alive
          cells[xCellOver][yCellOver]=0; // Kill
          fill(dead); // Fill with kill color
        }
        else { // Cell is dead
          cells[xCellOver][yCellOver]=1; // Make alive
          fill(alive); // Fill alive color
        }
      }
      else if (pause && !mousePressed) { // And then save to buffer once mouse goes up
        // Save cells to buffer (so we opeate with one array keeping the other intact)
        for (int x=0; x<width/cellSize; x++) {
          for (int y=0; y<height/cellSize; y++) {
            cellsBuffer[x][y] = cells[x][y];
          }
        }
      }
    }

    void iteration() { // When the clock ticks
      // Save cells to buffer (so we opeate with one array keeping the other intact)
      for (int x=0; x<width/cellSize; x++) {
        for (int y=0; y<height/cellSize; y++) {
          cellsBuffer[x][y] = cells[x][y];
        }
      }

      // Visit each cell:
      for (int x=0; x<width/cellSize; x++) {
        for (int y=0; y<height/cellSize; y++) {
          // And visit all the neighbours of each cell
          int neighbours = 0; // We'll count the neighbours
          for (int xx=x-1; xx<=x+1;xx++) {
            for (int yy=y-1; yy<=y+1;yy++) {
              if (((xx>=0)&&(xx<width/cellSize))&&((yy>=0)&&(yy<height/cellSize))) { // Make sure you are not out of bounds
                if (!((xx==x)&&(yy==y))) { // Make sure to to check against self
                  if (cellsBuffer[xx][yy]==1){
                    neighbours ++; // Check alive neighbours and count them
                  }
                } // End of if
              } // End of if
            } // End of yy loop
          } //End of xx loop
          // We've checked the neigbours: apply rules!
          if (cellsBuffer[x][y]==1) { // The cell is alive: kill it if necessary
            if (neighbours < 2 || neighbours > 3) {
              cells[x][y] = 0; // Die unless it has 2 or 3 neighbours
            }
          }
          else { // The cell is dead: make it live if necessary
            if (neighbours == 3 ) {
              cells[x][y] = 1; // Only if it has 3 neighbours
            }
          } // End of if
        } // End of y loop
      } // End of x loop
    } // End of function

    void keyPressed() {
      if (key=='r' || key == 'R') {
        // Restart: reinitialization of cells
        for (int x=0; x<width/cellSize; x++) {
          for (int y=0; y<height/cellSize; y++) {
            float state = random (100);
            if (state > probabilityOfAliveAtStart) {
              state = 0;
            }
            else {
              state = 1;
            }
            cells[x][y] = int(state); // Save state of each cell
          }
        }
      }
      if (key==' ') { // On/off of pause
        pause = !pause;
      }
      if (key=='c' || key == 'C') { // Clear all
        for (int x=0; x<width/cellSize; x++) {
          for (int y=0; y<height/cellSize; y++) {
            cells[x][y] = 0; // Save all to zero
          }
        }
      }
    }