How do i create a gravity flipping mechanic (ActionScript 3)

Question

Hi I am trying to make a game with gravity flipping as a mechanic much like the old miniclip game gravity guy but i cant seem to make it work. please help

This is the theory I have in my head. I have a movieclip and its always falling/this.y + dy. But once it collides with the platform dy will be set to 0 so it will stop falling. Then when i press the space bar, dy will be set to 3 again but it will multiply by -1 so it will start flying upwards instead.

This is what i have so far

package  {
import flash.display.*;
import flash.events.*;
import flash.ui.Keyboard;

public class Player extends MovieClip{
    //Properties
    private var moveLeft:Boolean;
    private var moveRight:Boolean;
    private var gravity:Boolean; //Switches gravity
    private var dx:Number //Speed of player moving on X axis
    private var dy:Number //Speed of player moving on Y axis
    private var level:MovieClip;
    private var platforms:Array;
    private var tilesTop:Array;
    private var tilesBtm:Array;
    private var tilesLeft:Array;
    private var tilesRight:Array;
    private var grounded:Boolean;
    private var flipGravity:Number;

    //Constructor
    public function Player(iMain:Main) {
        level = iMain.getLevel();
        platforms = level.getPlatforms();
        tilesTop = level.getTilesTop();
        tilesBtm = level.getTilesBtm();
        tilesLeft = level.getTilesLeft();
        tilesRight = level.getTilesRight();

        dx = 10;
        dy = 10;
        flipGravity = -1;
        this.addEventListener(Event.ADDED_TO_STAGE, addedToStageHandler);
    }

    //Methods
    // Method: Add to stage handler
    private function addedToStageHandler(evt:Event):void {
        this.stage.addEventListener(KeyboardEvent.KEY_DOWN, keyDownHandler);
        this.stage.addEventListener(KeyboardEvent.KEY_UP, keyUpHandler);
    }

    //Methods: Key down handler
    private function keyDownHandler(evt:KeyboardEvent):void {
        if (evt.keyCode == Keyboard.LEFT) {
            moveLeft = true;
        }
        else if (evt.keyCode == Keyboard.RIGHT) {
            moveRight = true;
        }
        else if (evt.keyCode == Keyboard.SPACE) {
            if (gravity) {
                gravity = false;
            }
            else if (!gravity) {
                gravity = true;
            }
        }
    }

    //Methods: Key up handler
    private function keyUpHandler(evt:KeyboardEvent):void {
        if (evt.keyCode == Keyboard.LEFT) {
            moveLeft = false;
        }
        else if (evt.keyCode == Keyboard.RIGHT) {
            moveRight = false;
        }
    }

    //Methods: Move player
    public function movePlayer() {

        // Move downward
        this.y += dy;

        grounded = false;

        // *** Player's collision tests
        // Check if it lands on platform
        landOnPlatform();

        // Move left
        if (moveLeft) {  // equivalent to if (moveLeft == true)
            if (this.x > 200) { //move player
                this.x -= dx;
            }
            else {
                level.moveLevel(dx);
                if  ( level.x >= 0 ) {//stage stop moving so that the player won't fall of the screen(left)
                    level.x = 0;
                    this.x -= dx;
                    if  (this.x < this.width/2) {
                        this.x=this.width/2;
                    }
                }
            }
        }

        // Move right
        if (moveRight) {
            if (this.x < 600) { //move player
                this.x += dx;
            }
            else {
                level.moveLevel(-dx);
                if (level.x <= -1600) { //stage stop moving so that the player won't fall of the screen(right)
                    level.x = -1600;
                    this.x += dx;
                    if  (this.x > stage.stageWidth - this.width/2) {
                        this.x= stage.stageWidth - this.width/2;
                    }
                }
            }
        }

        //Gravity flip
        if (!gravity) {
            dy *= flipGravity;
            grounded = false;
        }
    }

    private function landOnPlatform() {
        for (var i:int=0;i<platforms.length;i++) {
            /*if (this.hitTestObject(platforms[i])) {
                dy = 0;
                grounded = true;
                this.y = platforms[i].y;
                break;
            }*/
            if (this.hitTestObject(tilesTop[i])) {
                dy = 0;
                grounded = true;
                this.y = tilesTop[i].y;
                break;
            }

            else if (this.hitTestObject(tilesBtm[i])) {
                dy = 0;
                grounded = true;
                this.y = tilesBtm[i].y;
                break;
            }

            else if (this.hitTestObject(tilesLeft[i])) {
                dy = 0;
                grounded = true;
                this.x = tilesLeft[i].x;
                break;
            }

            else if (this.hitTestObject(tilesRight[i])) {
                dy = 0;
                grounded = true;
                this.x = tilesRight[i].x;
                break;
            }
        }
    }
}
}

This is the player class above

I have a gameloop running in the main class and its calling the function of move player.

So when gravity is false, the player will float up and when gravity is true the player will drop down. I wrote the code for when dy multiplies with -1 already but when i press space nothing seems to happen

This is all the files i have. Link

@jacksonecac I edited the question sorry. The question is how can i create a gravity flipping mechanic in game much like an old game called gravity guy — Gabriel Chan

Neal Davis Neal Davis · Accepted Answer · 2017-01-20T18:34:19

You need to change

dy * flipGravity;

to

dy *= flipGravity;

Simple typo? Or should I explain further? Probably a simple typo as I see you have been using += operators elsewhere. This is just like that but with multiplication.

How do i create a gravity flipping mechanic (ActionScript 3)

1 Answers