cn-sensei-guides/04-green/01-rooftop-runner.js

// Setting the Scene
// Common error is that ninjas add the asset to an existing asset thereby creating a unintended group. 
// Teach ninjas to always go back to the scene before pressing the add asset button.

// It's very easy for ninjas to neglect to set roles or speedX, or other properties because they are only looking
// at pictures in the manual. When reading carefully, they should notice that the manual
// asks SpeedX, roles, and positions (x,y, z) are provided for every object

// background z 0
// rooftop z 1
// runner z 5 (higher than rooftops) ensures that it shows up on top

//**************************** rooftop1 - Update Every Frame ********************************/
// rooftop is always moving 
// ensure speedX is set to -200 
$this.moveX();

if($this.x() <= -800) {
    $this.x(1200);
    $this.y(random(550,300));
}

//*************************** rooftop1 - Initialize When Scene Starts ***********************/
// sets initial rooftop x and randomizes y (height)
$this.x(0);
$this.y(random(550, 300));

//*************************** rooftop2 - Update When Scene Starts ***************************/