int corna = 10; int cornb = 10;
float side = 3;
void setup(){
  size(500,500);
  doPlot();
}

void draw(){
}

void mousePressed(){
  mouseDragged();
}
void mouseDragged(){
  side = 500 - mouseY;
  doPlot(); 
}

int steps = 100;
int sqsize = 500 / steps;


void doPlot(){
  float colorbase = map(mouseX,0,500,0,999);
  colorbase = constrain(colorbase,0,999);
  
  float r = map(floor(colorbase / 100),0,9,0,255);
  colorbase %= 100;
  float g = map(floor(colorbase / 10),0,9,0,255);
  colorbase %= 10;
  float b = map(colorbase,0,9,0,255);
  
  background(r,g,b);
  fill((r+128) % 256,(g+128) % 256,(b+128) % 256);
  
  

  noStroke();
 for(int i = 0; i < steps; i++){
    for(int j = 0; j < steps; j++){
      float x = (i) * side / steps;
      float y = ( j) * side / steps;
      int c = round((x*x)+(y*y));

      if(c % 2 == 0 ){
        rect(i*sqsize,j*sqsize,sqsize,sqsize);
      }   

    }
  } 
}