//// 080214a cr by rha on thales2 with P 0135 beta
//// follow R&F handbook p. 179

// 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);
  drawX(); // do the shape
  ex = ex + 1; // incr erase each frame
}

void drawX(){
  stroke(255); // white on black is classic
  if (ex < dx){
    line(x0 + ex, y0, x0 + dx, y0); // first step
    line(x0 + dx, y0, x0 + dx, y0 + dy); // fixed riser
    line(x0 + dx, y0 + dy, x0 + dx + ex, y0 + dy); // second step
  }
}

//// end