Example from Programming for Visual Artists class 2015-09-22

centipede.pde

// Centipede
// Steve Lambert
// September 23, 2015
// v0.1

int xPos = 15; // global variable
float greg = 15; // initialized at 15, so it shows up where I want it the first time

void setup() {
  size(500,500);
  smooth();
  noStroke();
//  frameRate(1); // can uncomment to slow things down for testing.
} // end setup

void draw() {
     background(255,0,0); 
      fill(255);


// CHECK OUT MY WHILE LOOP!
// IT DRAWS A ROW OF CIRCLES!!!!

     while (greg < width){ // Because I don't want to draw circles beyond the canvas
 
      fill(255);
      ellipse(greg,15,30,30);
      greg = greg + 30; 
      
     } // end of loop

        if (greg > width ){
        greg = 15;
        } // end of if statement       


// CHECK OUT MY FOR LOOP!
// IT DRAWS ANOTHER ROW OF CIRCLES!!!!

for (int i = 0; i < 12; i++) { // I want to make 12

  println ("i: " + i); // this shows me where we're at in the count

  ellipse(xPos,45,30,30); // this draws the circle
  
  xPos = xPos + 30;     // this moves makes the next cycle of the loop draw the circle to the right
  println("xPos: " + xPos); // this tells me where it will be
  
  } // end of for loop
 
//   if (xPos > 20 ){ // after the loop draws 12 times, this resets the xPos
    xPos = 15;
//    } // end of if statement
 

} // end of draw