int a,b,ac,bc;
void setup(){
  size(500,500);
  noStroke();
  ellipseMode(CORNER);
}
void draw(){
  for(int i=0;i<=20;i++){
      for(int j=0;j<=20;j++){
        a=i*25;
        b=j*25;
        ac=a/2;
        bc=b/2;
        if((i+j)%2==0){
          fill(ac+mouseY,bc+mouseY,mouseX);
        }else{
          fill(255-(ac+mouseY),255-(bc+mouseY),mouseX);
        }
        rect(a,b,25,25);
        if((i+j)%2==0){
          fill(255-ac,255-bc,(mouseX+mouseY)/2);
          rect(a+5,b+5,15,15);
        }else{
          fill(ac,bc,(mouseX+mouseY)/2);
          ellipse(a+5,b+5,15,15);
        }
      }
  }
}