int windowsize=300;

void setup()
{
  size(windowsize, windowsize);
  background(255);
  // frameRate(20);
  loop();
}

void draw()
{
 int n=mouseX/10;
 int m=mouseY/10;
 fill(255);
 rect(0,0,windowsize,windowsize);
 federico(13,n,0,1);
 federico(13,m,0,1);
}

void federico(int a, int b, int c, int d)
{
noStroke();  
float sidelength = 9;
  
for(int i=-200; i<=200; i+=10) {
for(int j=-200; j<=200; j+=10) {
  
  
  //identity times matrix  
  fill(0,160,200);
  rect(a*i+b*j+windowsize/2,c*i+d*j+windowsize/2,sidelength,sidelength);

  // alpha times matrix
  fill(0,140,180);
  rect(c*i+d*j+windowsize/2, -a*i-b*j+windowsize/2,sidelength,sidelength);

  // beta times matrix
  fill(0,120,160);
  rect(c*i+d*j+windowsize/2, a*i+b*j+windowsize/2,sidelength,sidelength);

  // alpha beta times matrix
  fill(0,100,140);
  rect(a*i+b*j+windowsize/2, -c*i-d*j+windowsize/2,sidelength,sidelength);
}
}
}