How to optimize a acceleration / friction function more

Question

Hello !
In few words what the code does:
It starts rotating from a speed of 2 deg and for 5 secs it accelerates to 20 deg per sec.
after that , the speed of rotation stays 20deg  for 10 secs and after the 10 secs are over
it gets in the friction function where it slows down back to 2deg a sec.
but ! as I am not that good with optimization and writing clean code I see myself in a need to ask if this is a good code or it can be done even better (more optimized and cleaner).
The code is this :
Box() is a simple box shape ,nothing more
          import flash.display.MovieClip;
          import flash.events.Event;
          public class Main extends MovieClip
                    protected var _box:Box = new Box();
                    private var fps:Number = stage.frameRate;
                    private var step:Number = 20;
                    private var minStep:Number = 2;
                    private var time:Number = 5;
                    private var increment:Number = (step - minStep) / (time * fps);
                                                                                          // 20 - 2 / 5 * 30
                                                                                          // 18 / 150
                                                                                          // 0.12
                    protected var timePassed:Number = 0
                    public function Main()
                              _box.x = stage.stageWidth/2 - _box.width/2;
                              _box.y = stage.stageHeight/2 - _box.height/2;
                              this.addChild(_box);
                              stage.addEventListener(Event.ENTER_FRAME, constantMovement);
                    private function friction():void
                               _box.rotation += step;
                                  step -= increment;
                                  step = Math.max(2, step);
                    private function acceleration():void
                               _box.rotation += minStep;
                               minStep += increment;
                               minStep = Math.min(minStep, 20);
                    private function constantMovement(event:Event)
                              if(minStep < 20)
                                        acceleration()
                              else if(minStep >= 20 && timePassed <= 10)
                                        _box.rotation += 20;
                                        timePassed += 10 / (time * fps)
                                        trace("timePassed :" + timePassed)
                              else if (minStep >= 20 && timePassed >= 10)
                                        friction();
If there is something more it can be done please tell me/ help me.

Answer 1

You can do the following:
1. Replace the last else if (minStep >= 20 && timePassed >= 10) with simply else, as the condition would always be true if control reaches there.
2. Store the value 10 / (time * fps) in a private variable and use that directly, rather than evaluating it each time as the value remains constant.
You can also try replacing the if-else-if block with a switch-case block on a state variable in the class (with values as 0, 1, 2 signifying accelerating, constant speed and decelerating, you can define symbolic constants to hold the values). Initialize the variable with value 0 (accelerating), change it to 1 when minStep becomes 20 and so on. Point#2 still holds good in this case too.
-Dharmendra