This example is for Processing 3+. If you have a previous version, use the examples included with your software. If you see any errors or have suggestions, please let us know.

A Processing implementation of Game of Life By Joan Soler-Adillon * Press SPACE BAR to pause and change the cell's values with the mouse On pause, click to activate/deactivate cells Press R to randomly reset the cells' grid Press C to clear the cells' grid * The original Game of Life was created by John Conway in 1970.

```
// 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);

// 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 {
}
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
}
}
}
}

```