Here's the code to make this happen.
function add_all_my_pipes() {
add_pipe(500, 100, 140);
add_pipe(800, 50, 140);
add_pipe(1000, 250, 140);
var finish_line = new MySprite("http://s2js.com/img/etc/flappyend.png");
finish_line.x = 1200;
finish_line.velocity_x = pipe_speed;
pipes.push(finish_line);
}
The really cool thing is
that's all the code required.
The logic to slide the finish line closer and to end the game when the finish line is reached is already in what we've done.