Code in frame 1 layer 1

//two planets

//simulate a space ship no friction

//add a planet with basic gravity

//experiment with a second planet



init();



function init(){

  //create the ship



  myShip.dx = 0;

  myShip.dy = 0;

  myShip.speed = 0;

  myShip.dir = 0;

  myShip.gotoAndStop("still");



  planet.gravity = 10000;

  planet2.gravity = 15000;



  //set up drawing

  _root.moveTo(myShip._x, myShip._y);

  _root.lineStyle(.5,0xffffff,100);



} // end init



myShip.onEnterFrame = function(){

  myShip.checkKeys();

  myShip.turn();

  myShip.move();

  myShip.gravitate(planet)

  myShip.gravitate(planet2)

} // end enter frame



myShip.checkKeys = function(){

  //check for left and right arrows

  if (Key.isDown(Key.LEFT)){

    this.dir -= 10;

    this.gotoAndStop("left");

    if (this.dir < 0){

      this.dir = 350;

    } // end if

  } else if (Key.isDown(Key.RIGHT)){

    this.dir += 10;

    this.gotoAndStop("right");

    if (this.dir > 360){

      this.dir = 10;

    } // end if

  } else if (Key.isDown(Key.UP)){

    //thrust on up arrow

    this.thrustSpeed = 1;

    this.gotoAndPlay("thrust");

  } else {

    this.thrustSpeed = 0;

    this.gotoAndStop("still");

  } // end if



  if (Key.isDown(Key.SPACE)){

    //clear drawings

    _root.clear();



    //restart drawing

    _root.moveTo(myShip._x, myShip._y);

    _root.lineStyle(.5,0xffffff,100);



  } // end if

} // end checkKeys



myShip.turn = function(){

  this._rotation = this.dir;

  //trace("I'm here...");



  //get new thrust vector

  degrees = this.dir

  degrees -= 90;

  radians = degrees * Math.PI / 180;

  thrustDX = this.thrustSpeed * Math.cos(radians);

  thrustDY = this.thrustSpeed * Math.sin(radians);



  //add thrust to dx and dy

  this.dx += thrustDX;

  this.dy += thrustDY; 



} // end turn



myShip.move = function(){

  this._x += this.dx;

  myShip._y += this.dy;



  //  let ship go off screen



  _root.lineTo(this._x, this._y);



} // end move



myShip.gravitate = function(focus){

   //pull this element to the focus object

   //assumes focus object has a gravity property



   //figure angle difference between ship and planet

   tempDX = this._x - focus._x;

   tempDY = this._y - focus._y;



   //calculate distance between ship and planet

   tempDistance = Math.sqrt(tempDX * tempDX + tempDY * tempDY);



   //normalize vector (make it length of one)

   tempDX /= tempDistance;

   tempDY /= tempDistance;



   //compensate for the planet’s gravitational pull

   tempDX *= focus.gravity / (tempDistance * tempDistance);

   tempDY *= focus.gravity / (tempDistance * tempDistance);



   //invert the vector so it pulls ship to planet

   tempDX *= -1;

   tempDY *= -1;



   //add vector to ship

   this.dx += tempDX;

   this.dy += tempDY;

} // end gravitate