Moving Platforms

package;

import flixel.FlxG;
import flixel.FlxObject;
import flixel.FlxSprite;
import flixel.FlxState;
import flixel.tile.FlxTilemap;
import flixel.ui.FlxVirtualPad;
import flixel.util.FlxAxes;

class PlayState extends FlxState
{
    var map:FlxTilemap;
    var platform:FlxSprite;
    var sprite:FlxSprite;
    var pad:FlxVirtualPad;

    override public function create()
    {
        super.create();

        map = new FlxTilemap();
        map.loadMapFromCSV("assets/platform.csv", "assets/tiles.png", 16, 16);
        add(map);

        platform = new FlxSprite();
        platform.loadGraphic("assets/bigbox.png");
        platform.velocity.set(100, 0);
        platform.immovable = true;
        platform.screenCenter(FlxAxes.X);
        platform.y = 16 * 8;
        add(platform);

        sprite = new FlxSprite();
        sprite.loadGraphic("assets/sprite.png");
        resetSprite();
        sprite.acceleration.y = 600;
        add(sprite);

        pad = new FlxVirtualPad(FlxDPadMode.LEFT_RIGHT, FlxActionMode.NONE);
        add(pad);
    }

    override public function update(elapsed:Float)
    {
        super.update(elapsed);

        if (map.overlaps(platform))
            platform.velocity.x *= -1;
        FlxG.collide(map, sprite);

        FlxG.collide(platform, sprite);

        if (sprite.y >= FlxG.height - (16 * 3))
            resetSprite();

        var left:Bool = pad.buttonLeft.pressed || FlxG.keys.anyPressed([A, LEFT]);
        var right:Bool = pad.buttonRight.pressed || FlxG.keys.anyPressed([D, RIGHT]);

        if (left && right)
            left = right = false;
        if (left)
            sprite.velocity.x = -100;
        else if (right)
            sprite.velocity.x = 100;
        else
            sprite.velocity.x = 0;
    }

    function resetSprite()
    {
        sprite.x = platform.x + (platform.width / 2) - (sprite.width / 2);
        sprite.y = platform.y - sprite.height;
    }
}