How to make a vertical lift or elevator in a platform game

Question

I am creating a side scrolling platform game using the book "Flash Game University" by Gary Rosenzweig.
My protagonist has an instance of "hero".
My current issue is trying to create a lift or elevator to carry the player up or down. The lift is not covered in the book. My thoughts were that the lift constantly moved up and down at a pace determined by a timer. I cannot get my lift to move. I have created a movie clip called "lift" and made it exported for action script. I can make it act similar to a floor movie clip so that I can stand on it, but I cannot get the lift to move on the y axis.
I tried creating a new function called lift() and using a for loop to count between 0 and 100 using a variable "i" and then make my lift move up 1 unit for each loopcycle. It didn't work.
lift.y -= lift.y - 1;
Does anyone have a better solution?
Thanks,
Alex

Answer 1

Rob,
This worked. Here is my current code ...
var topIndex:Number = 20;
                    var bottomIndex:Number = 160;
                    var stepDistance:Number = 10;
                    var movingUp:Boolean = true;
public function createLift()
                                        box = new Object();
                                        box.mc = gamelevel.box;
public function moveMyLift():void
                                        // lift 01
                                        if (movingUp && box.mc.y > topIndex)
                                                  box.mc.y -= stepDistance;
                                        else
                                                  movingUp = false;
                                          if (!movingUp && box.mc.y < bottomIndex)
                                                  box.mc.y += stepDistance;
                                        else
                                                  movingUp = true;
                                        if (hero.mc.hitTestObject(box.mc))
                                                  hero.mc.y = box.mc.y;
My lift works correctly. It moves up and down correctly and when I jump on it I stay moving on it. There are only 3 things that don't make sense.
1. When I am on the elevator I cannot jump. If I am not on the elevator I can jump normally.
2. When I touch any portion of the elevator, my character automatically repositions itself to stand on the elevator. It seems normal, but not something that should happen in my scenario. I only want to "climb" on the elevator if I touch the "top" of the elevator.
3. If I add a second elevator, even with its own function, the timing of the elevator math appears to synch instead of work independently. Why? The two elevators synch their movement and timing. Also the first elevator stutters as the synching of the two elevators match thier movement and then moves in unison with the second elevator. Why are they not operating separately?
Here is the code for the first and second elevator:
private var box:Object;
private var box02:Object;
var topIndex:Number = 20;
var bottomIndex:Number = 160;
var stepDistance:Number = 10;
var movingUp:Boolean = true;
var topIndexLift02:Number = 1;
                    var bottomIndexLift02:Number = 100;
                    var stepDistanceLift02:Number = 4;
public function createLift()
                                        box = new Object();
                                        box.mc = gamelevel.box;
                                        box02 = new Object();
                                        box02.mc = gamelevel.box02;
public function moveMyLift():void
                                        // lift 01
                                        if (movingUp && box.mc.y > topIndex)
                                                  box.mc.y -= stepDistance;
                                        else
                                                  movingUp = false;
                                          if (!movingUp && box.mc.y < bottomIndex)
                                                  box.mc.y += stepDistance;
                                        else
                                                  movingUp = true;
                                        if (hero.mc.hitTestObject(box.mc))
                                                  hero.mc.y = box.mc.y;
                              public function moveMyLift02():void
                                        // lift02
                                        if (movingUp && box02.mc.y > topIndexLift02)
                                                  box02.mc.y -= stepDistanceLift02;
                                        else
                                                  movingUp = false;
                                          if (!movingUp && box02.mc.y < bottomIndexLift02)
                                                  box02.mc.y += stepDistanceLift02;
                                        else
                                                  movingUp = true;
                                        if (hero.mc.hitTestObject(box02.mc))
                                                  hero.mc.y = box02.mc.y;
public function gameLoop(event:Event)
                                        // get time difference
                                        if (lastTime == 0) lastTime = getTimer();
                                        var timeDiff:int = getTimer() - lastTime;
                                        lastTime += timeDiff;
                                        // only perform tasks if in play mode
                                        if (gameMode == "play")
                                                  moveCharacter(hero,timeDiff);
                                                  moveEnemies(timeDiff);
                                                  checkCollisions();
                                                  scrollWithHero();
                                                  createLift();
                                                  moveMyLift();
  moveMyLift02();
Thank you,
Alex
Message was edited by: ajdove