Top-Down RPG Shooter — Part 2 — Player Movement

Welcome back to the second part of my “Top-Down RPG Shooter” flash game tutorial. In the last part, we set up a new project and linked it to an external Document Class, and we added the Player to the stage. In this tutorial, we’re going to program keyboard controls to move the player.

Step 1: KeyObject.as

We are going to make use of a really great open-source class called “KeyObject.as“. This class was written by a talented developer named senocular. It provides a really simple but powerful way to check which keyboard keys are pressed.

Copy and paste this class into a new .as actionscript file, and save it as “KeyObject.as” in the same folder as your main project:

package {

	import flash.display.Stage;
	import flash.events.KeyboardEvent;
	import flash.ui.Keyboard;
	import flash.utils.Proxy;
	import flash.utils.flash_proxy;

	/**
	 * The KeyObject class recreates functionality of
	 * Key.isDown of ActionScript 1 and 2
	 *
	 * Usage:
	 * var key:KeyObject = new KeyObject(stage);
	 * if (key.isDown(key.LEFT)) { ... }
	 */
	dynamic public class KeyObject extends Proxy {

		private static var stage:Stage;
		private static var keysDown:Object;

		public function KeyObject(stage:Stage) {
			construct(stage);
		}

		public function construct(stage:Stage):void {
			KeyObject.stage = stage;
			keysDown = new Object();
			stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressed);
			stage.addEventListener(KeyboardEvent.KEY_UP, keyReleased);
		}

		flash_proxy override function getProperty(name:*):* {
			return (name in Keyboard) ? Keyboard[name] : -1;
		}

		public function isDown(keyCode:uint):Boolean {
			return Boolean(keyCode in keysDown);
		}

		public function deconstruct():void {
			stage.removeEventListener(KeyboardEvent.KEY_DOWN, keyPressed);
			stage.removeEventListener(KeyboardEvent.KEY_UP, keyReleased);
			keysDown = new Object();
			KeyObject.stage = null;
		}

		private function keyPressed(evt:KeyboardEvent):void {
			keysDown[evt.keyCode] = true;
		}

		private function keyReleased(evt:KeyboardEvent):void {
			delete keysDown[evt.keyCode];
		}
	}
}

How do we use this class? Basically, we’re going to create an instance of it called “key” in our Player class (or wherever we need to access the keyboard controls). Then in that class, we can check the Boolean value of the keyObject’s isDown() function for specific keys. We can refer to keys by their unique keyCode. For example, if key.isDown(65) returns true, it means that the “A” keyboard key is currently being pressed.

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News! AS3GameTuts Discussion Board

After some debate, I’ve decided to create a discussion board for AS3GameTuts.com

It’s a simple, free forum, but I think it will do a good job at expanding the “comment” sections of this site.

You can find it here: http://as3gametuts.forumatic.com/

Hello Everyone, and welcome to AS3GameTuts’ new discussion board!

When I first started the AS3GameTuts website, I had only a few readers, and so it was easy for me to answer everyone’s questions, and respond to each comment individually. But now, the number of comments and support emails I am receiving is making it impossible to give everyone the attention I’d like to. This forum is how I’m attempting to solve this problem.

By creating an open, shared, easily-navigable discussion board, I am hoping that you will all have an easier time finding answers to your questions. Maybe you will find that someone has had a similar problem to your own, and found a solution. Or perhaps you can help another reader with a problem of their own.

This is also a great place to hear the latest news about the site, and to leave me a suggestion about future tutorials you would like to see written on AS3GameTuts.

Anyways, thanks for all your support, and welcome to the forum!

 

Please join the AS3GameTuts community on this discussion board, and let me know what you think!

Ben Reynolds

Sidescrolling Platformer — Part 12 — Basic Enemies

Welcome back to the side scrolling tutorial series. In this session, we will be adding (very) basic enemies to the game, which you can shoot and destroy with the bullets we created previously. This will create a lot of possibilities for what you can do with your game. In later tutorials we will add a scoring system and more advanced A.I. (artificial intelligence) to the enemies, but for now let’s focus on: creating the Enemy class, adding a few enemies to the game map, and destroying them when they are hit by a bullet.

Creating the Enemy Class

Creating the Enemy class is very similar to creating the Bullet class. If you just read Part 10 and Part 11, most of this step will look the same as when we made the Bullet class and symbol.

First, we need art. We need to create a Movie Clip object to represent the enemy on the stage. Feel free to decorate your enemy however you choose — it could be a random, inanimate object, a crazy monster, or anywhere in between.

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Sidescrolling Platformer — Part 11 — Fixing the bullets

Although we did get some functional bullets last time by using the Bullet class, we still need to make some major improvements. First of all, the bullets are added directly to the stage and have no idea about the scrollX and scrollY variables, so they don’t react when the player moves left, right, up, or down. Also, the bullets move at a sluggish pace — if they did react to the player’s movements, you could practically outrun them. Finally, they are never actually removed from the stage, so we waste precious memory that slows down the game. Imagine that we fired 1,000,000 bullets. The game would still be keeping track of all of them, constantly updating their positions, even if they are no longer on the stage. There’s some more code we can add to the bullets to handle all of this, and we are going to implement it in this tutorial.

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Sidescrolling Platformer — Part 10 — Shooting

Welcome back to the flash game tutorial: how to make a side scrolling platformer game in actionscript 3. I can’t believe we’re already up to part ten! As you can probably tell from the title, this tutorial part will exclusively feature shooting. Not all platformer games require this feature, but I’ve had a bunch of requests for this tutorial — probably because side scrolling shooters are an amazing game genre (for example, the classic Metroid games). We don’t have anything yet for our bullets to interact with, but don’t worry — next tutorial we will add the enemies. For now, let’s just focus on getting our hero to shoot.

Here is a preliminary demo of what we’ll be creating. Use the space bar to fire.

An External Actionscript File

…I knew this moment would arrive eventually… the moment when — *gasp* — we finally need to use a custom class and an external actionscript file. If you’ve never programmed anything with Object Oriented Programming before, and you’ve never created an external .as file, this might seem intimidating. Or perhaps you have no idea what I’m talking about. No matter where you stand right now, I hope that by the end of this tutorial you will have a solid idea of what external classes are, why we use them, and how to create a Class for the bullets. In future tutorials we will go into more depth on the topic.

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Sidescrolling Platformer — Part 9 — Animated Player Movements

All great platformers have animated heroes. Even Super Mario, which was released in 1985, used several animations for the player. Why? Because it would look completely unrealistic if Mario just stood frozen in one animation while he runs and jumps around the level. So it makes sense that we should add animations to our player. This will add yet another step of realism to the game.

Try running, jumping, or standing still. See how the player’s animation state reacts:

My art could definitely be improved, but I’ll demonstrate how to create these 3 animations for simplicity’s sake.

The Structure

The most important aspect of giving any game element multiple animation states, is to make sure you structure it correctly. When I first started programming, I tried to put all of the animations on a single timeline, and the resulting structure was too cluttered and complicated that it was difficult to make things work the way I wanted them to. So now I’m sharing with you a simpler method.

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Sidescrolling Platformer — Part 8 — Multiple Levels

Here’s the post you’ve all been waiting for… how to connect multiple levels in your platformer!

Try out this demo. Press the down arrow key upon opening the door to warp to the next level:

After adding the door and key last time, the next step is to make the door lead to the next level. “How?”, you might ask… just read on to see the magic unfold.

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