GMU:Actors, Traces, Collectives/SS17/Schachbrettmuster Array

int  [][] rectPos;

void setup () {
  size (800, 800);
  noLoop();

  rectPos = new int [width/20][height/20];
}

void draw() {

  for (int j = 0; j < height /20; j ++) {
    for (int i =0; i < width/20; i ++) {

      rectPos [i][j] = rectPos [i][j] + 20*i;
      
      if (i%2==0&&j%2==0) {
        fill(0);
      }else if(i%2!=0&&j%2!=0){
        fill(0);
      }else{
      fill (255);
      }
       rect (i*20, j*20, 20, 20 );
    }
  }
}