pixelated screensaver sand hourglass sketch you can control

controllable_sand_sketch.java

import java.awt.*;
  
  private PImage orig;
  private int effScl = 3; //effect scale used heaping pixels into groups to ease processor's burden
  private float yForce = 0.95f; //values from 0 to 1
  private float xForce = 0.95f; //values from 0 to 1
  
  public void settings()
  {
      fullScreen();
      orig = screenshot();
  }
  
  public void setup(){
      image(orig, 0, 0,width, height);
      frameRate(30);
  }
  
  public void draw()
  {
      checkInput();
      modifyPixels();
      //println(frameRate);
  }
    
  private void modifyPixels(){
      loadPixels();
      for(int x = 0; x < width/ effScl; x++) {
          for (int y = 0; y < height/ effScl; y++) {
              int force = getForce();
              //for each virtual square on my screen with side length "effScl"
              for(int xOff = 0; xOff < effScl; xOff++){
                  for(int yOff = 0; yOff < effScl; yOff++){
                      if(force == 0)  shiftU(x*effScl + xOff, y*effScl + yOff);
                      if(force == 1)  shiftD(x*effScl + xOff, y*effScl + yOff);
                      if(force == 2)  shiftL(x*effScl + xOff, y*effScl + yOff);
                      if(force == 3)  shiftR(x*effScl + xOff, y*effScl + yOff);
                  }
              }  
          }
      }
      updatePixels();
  }
  
  int getForce(){
      int force;
      if(coinFlip(0.5f)){
          if(coinFlip(yForce)) force = 0;
          else force = 1;
      }else{
          if(coinFlip(xForce)) force = 2;
          else force = 3;
      }
      return force;
  }
  
  public void checkInput(){
      xForce = map(mouseX,0, width, 0.01f, .99f);
      yForce = map(mouseY,0, height, 0.01f, .99f);
  }
  
  public void keyPressed(){
      if(key == 'm') effScl++;
      if(key == 'n' && effScl > 1) effScl--;
  }
  
  private void shiftU(int x, int y){
      if(getPixel(x, y) > getPixel(x, y+1)){
          swapPixels(x, y, x, y+1);
      }
  }
  
  private void shiftD(int x, int y){
      if(getPixel(x, y) > getPixel(x, y-1)){
          swapPixels(x, y, x, y-1);
      }
  }
  
  private void shiftR(int x, int y){
      if(getPixel(x, y) > getPixel(x-1, y)){
          swapPixels(x, y, x-1, y);
      }
  }
  
  private void shiftL(int x, int y){
      if(getPixel(x, y) > getPixel(x+1, y)){
          swapPixels(x, y, x+1, y);
      }
  }
  
  private boolean coinFlip(float odds){
      return random(1) < odds;
  }
  
  private void swapPixels(int x0, int y0, int x1, int y1){
      //boundary check
      if(x0 < width && x0 >= 0 && y0 < height && y0 >= 0
              && x1 < width && x1 >= 0 && y1 < height && y1 >= 0){
          int rem = getPixel(x0, y0);            // remember  0
          setPixel(x0, y0, getPixel(x1, y1));    // overwrite 0
          setPixel(x1, y1, rem);                 // overwrite 1
      }
  }
  private int getPixel(int x, int y){
      int index = x + y * width;
      if(index < pixels.length && index >= 0){
          return pixels[index];
      }
      return 0;
  }
  
  private void setPixel(int x, int y, int clr){
      int index = x + y * width;
      if(index < pixels.length && index > 0){
          pixels[x + y * width] = clr;
      }
  }
  
  private PImage screenshot() {
      PImage screenshot = null;
      try {
          screenshot = new PImage(new Robot().createScreenCapture(
                  new Rectangle(0, 0, displayWidth, displayHeight)));
      } catch (AWTException e) {
          e.printStackTrace();
      }
      return screenshot;
}