////080220c, build upon 080220a, a slinky
// add offset args

// get some variables (dimensions of our angle)
int x0 = 50; // have to declare the type in P
int y0 = 100; // have to declare the type in P
int dx = 50; // width of step
int dy = 50; // height of riser
int ex = 0; // length to erase

// setup the canvas
void setup(){
  size(400, 300); // do not want to change this later
  background(0); // black is nice for a movie/}
  frameRate(5); // slow
}

// draw some lines
void draw(){
  background(0);
  draw1(0, 0); // do the shape
  ex = ex + 1; // incr erase each frame
}

void draw1(int cx, int cy){
  stroke(255, 255, 0); // yellos on black is nicer
  noFill();
  smooth();
  strokeWeight(10.0);
  strokeJoin(MITER);
  int u = x0 + cx; // offset x
  int v = y0 + cy; // offset x
  if (ex < dx){
    beginShape();
      vertex(u + ex, v); // x0 + dx, y0); // first step
      vertex(u + dx, v); // x0 + dx, y0 + dy); // fixed riser
      vertex(u + dx, v + dy); // ); // second step
      vertex(u + dx + ex, v + dy); // end point
    endShape();
  }
}

//// end