void draw() { fill(0); while (x < width) { // if x smaller than width while (x> width) { // x = 0 when program start, so i assumed that processing skip that while loop. y = y + 17 ; // if x greater than width, y must be +17. } rect(x, y, 15, 15); //draw 15*15 rectangle at x,y positions x = x + 17; } }