How To Select Units in an AS3 Game

In this tutorial, we will draw a selection rectangle with the mouse (as seen in strategy games such as StarCraft and Command and Conquer), and we will also learn how to select units with the rectangle!

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Final Result Preview

Let’s take a look at the final result we will be working towards:

Click and drag with your mouse to draw a rectangle that will select any soldier that it touches.

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Step 1: The Setup

If you are using Flash, create a new ActionScript 3.0 file with the size ’550 x 400′. However, if you are not using the Flash IDE and are using another such as FlashDevelop or Flash Builder, this tutorial contains the SWC files so you can use MovieClips from within your IDE of preference. If you are curious on how to import MovieClips with your IDE, check out the Beginner’s Guide to FlashDevelop and Beginner’s Guide to FDT!

I should also note that I have included the FLA file in case you do not wish to draw any of your own material.

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Step 2: Creating the Document Class

Ok, now you may be a little confused if you haven’t really worked with classes before. If you wish to learn more about why classes are important in programming, check out this article by kirupa, or this guide to the document class.

Create a new ‘ActionScript 3.0 Class’ and give it the name ‘SelectionDemo’. When the file has been created, save it as ‘SelectionDemo.as’. You should save files all the time. I can not stress this enough but the amount of times I have forgot to save work that I have done and lost it all doesn’t bear thinking about. So please, do save the files!

If you are using an IDE that generates the code for you when you create the class, you should have most of the code below. However, you must still add the lines that I have highlighted:

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