/// mod to ralph's slinky
/// not able to write any new math
/// just trying to get this done today...
/// sadly, g. craig hobbs

// get some variables (dimensions of our angle)
int x0 = 100; // have to declare the type in P
int y0 = 250; // have to declare the type in P
int dx = 25; // width of step
int dy = 25; // height of riser
int ex = 0; // length to erase

// setup the canvas
void setup(){
  size(400, 400); // do not want to change this later
  frameRate(10); // fast
}

// draw some lines
void draw(){
  PImage b;
  b = loadImage("stairwell.jpg");
  background(b);
  stroke(223, 20, 20); // 

  draw5();
  ex = ex + 1; // incr erase each frame
  // print(frameCount); // debug line
  if (frameCount == 10){
    ex = 0; // reset eraser
    stroke(223, 20, 20); // change color
    x0 = x0 + dx; // change position
    y0 = y0 + dy;
  }
  
    draw5();
  ex = ex + 1; // incr erase each frame
  // print(frameCount); // debug line
  if (frameCount == 20){
    ex = 0; // reset eraser
    stroke(223, 20, 20); // change color
    x0 = x0 + dx; // change position
    y0 = y0 + dy;
  }
  
  
    draw5();
  ex = ex + 1; // incr erase each frame
  // print(frameCount); // debug line
  if (frameCount == 30){
    ex = 0; // reset eraser
    stroke(223, 20, 20); // change color
    x0 = x0 + dx; // change position
    y0 = y0 + dy;
  }
  
      draw5();
  ex = ex + 1; // incr erase each frame
  // print(frameCount); // debug line
  if (frameCount == 40){
    ex = 0; // reset eraser
    stroke(223, 20, 20); // change color
    x0 = x0 + dx; // change position
    y0 = y0 + dy;
  }
  
}

void draw1(int cx, int cy){
  noFill();
  smooth();
  strokeWeight(2.0);
  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();
  }
}

void draw5(){
  draw1(0, 0); // do the shape
  draw1(10, -10); // do the shape  
  draw1(20, -20); // do the shape
  draw1(30, -30); // do the shape
  draw1(40, -40); // do the shape
  draw1(50, -50); // do the shape
}


//// end