/*
 * Draw some lines...
 *
 */
 
 // the initial spacing between lines, in pixels
 float spacing = 1f;
 
 // line width in pixels (from middle of line)
 float lineWidth = 1.5;
 
 // the multiplier for the spacing of successive lines
 float spaceMult = 1.001f;
 float startTime = 0f;
 
 
 void setup()
 {
     size(768, 512);
     background(0);
     strokeWeight(lineWidth);
     smooth();

     startTime = millis();
 }
 
 
 void draw()
 {
   background(0);
 
   //spaceMult = sin( (millis() - startTime)*0.0001f % PI)+1.0001f;  
   
   spaceMult = (millis() - startTime)*0.0002f % 1f + 1.00001f;  
   int iters = 0;
   
   int ctr=0;  // counter var
   float space = spacing;
   
   //first draw white bg below
   fill(255);
   noStroke();
   rect(0, 0, width, height*0.5);
   
   // draw black lines from center to top
   
   ctr = int(height*0.5-space);
   
   strokeWeight(lineWidth);
   stroke(0);
   
   while (ctr > 0 && iters < height)
   {
     iters++;
     line(0, ctr, width, ctr);
     ctr -= int(2*space);
     space *= spaceMult;
   }
   
   // draw white lines from center to bottom
   
   stroke(255);
   space = spacing;
   ctr = int(height*0.5-space);
   iters = 0;
   
   while (ctr < height && iters < height)
   {
     iters++;
     line(0, ctr, width, ctr);
     ctr += int(2*space);
     space *= spaceMult;
   }
   
   
   stroke(255);
   space = spacing;
   ctr = int(width*0.5-space);
   iters = 0;
   
   while (ctr < width && iters < width)
   {
     iters++;
     line(ctr, height*0.5, ctr, height);
     ctr += int(2*space);
     space *= spaceMult;
   }
   
   stroke(0);
   space = spacing;
   ctr = int(width*0.5-space);
   iters = 0;
   
   while (ctr > 0 && iters < width)
   {
     iters++;
     line(ctr, 0, ctr, height*0.5);
     ctr -= int(2*space);
     space *= spaceMult;
   }
   
   
 }