Home > Articles > Programming > Games

This chapter is from the book

Adding Game Effects

Gone are the early days of games on the Web, when just the idea of a game in a web page was cool enough to get you attention. Now, you have to work to add quality to your games—little touches such as animation and sound.

Let's spruce up this simple matching game with some special effects. Although they won't change the basic game play, they will make the game seem a lot more interesting to players.

Animated Card Flips

Because we are flipping virtual cards over and back, it makes sense to want to see this flip as an animation. You can do this with a series of frames inside a movie clip, but because you're learning ActionScript here, let's do it with ActionScript.

Because this animation affects the cards, and only the cards, it makes sense to put it inside the Card class. However, we don't have a Card class. We opted way back at the start of this chapter to not use a Card class and just allow Flash to assign a default class to it.

Now it is time to create Card class. If we make a Card.as file, however, it will be used by any Card object that is in the folder. We've already got MatchingGame1.fla through MatchingGame9.fla with Card objects in it. So, to make it clear that we only want MatchingGame10.fla to use this Card class, we'll change the name of the symbol, and the class it references, to Card10. Then, we'll create a Card10.as ActionScript class file.

This class will enable an animated flip of the card, rather than just changing the card instantly. It will replace all the gotoAndStop functions in the main class. Instead, it will tell the card to startFlip. It also passes in the frame which the card should show when the flip is over. The Card10 class will then set up some variables, set up an event listener, and proceed to animate the card over the next ten frames:

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

    public dynamic class Card10 extends MovieClip {
        private var flipStep:uint;
        private var isFlipping:Boolean = false;
        private var flipToFrame:uint;

        // begin the flip, remember which frame to jump to
        public function startFlip(flipToWhichFrame:uint) {
            isFlipping = true;
            flipStep = 10;
            flipToFrame = flipToWhichFrame;
            this.addEventListener(Event.ENTER_FRAME, flip);
        }

        // take 10 steps to flip
        public function flip(event:Event) {
            flipStep--; // next step

            if (flipStep > 5) { // first half of flip
                this.scaleX = .2*(flipStep-6);
            } else { // second half of flip
                this.scaleX = .2*(5-flipStep);
            }

            // when it is the middle of the flip, go to new frame
            if (flipStep == 5) {
                gotoAndStop(flipToFrame);
            }

            // at the end of the flip, stop the animation
            if (flipStep == 0) {
                this.removeEventListener(Event.ENTER_FRAME, flip);
            }
        }
    }
}

So, the flipStep variable starts at 10 when the startFlip function is called. It then is reduced by one each frame thereafter.

If flipStep is between 6 and 10, the scaleX property of the card is set to .2*(flipStep-6), which would be .8, .6, .4, .2, and 0. So, it gets thinner with each step.

Then, when flipStep is between 5 and 0, the new formula of .2*(5-flipStep) is used. So, it would be 0, .2, .4, .6, .8, and then 1.0; and so, it returns to normal size.

At the fifth step, the card jumps to the new frame. It appears to shrink, goes to nothing, jumps to the new frame, and then grows again.

To accomplish this effect, I had to make one change to how the graphics on the Card movie clip were arranged. In all previous versions of the game, the cards had their upper-left corner at the center of the movie clip. For the change to scaleX to make it appear that the card was flipping around its center, however, I had to center the card graphics on each frame over the center of the movie clip. Compare the Card movie clips in MachingGame9.fla and MatchingGame10.fla to see the difference. See Figure 3.16 to see how this looks when editing the movie clips.

Figure 3.16

Figure 3.16 The left side shows the registration point of the movie clip at the upper left, as it is in the first nine example movies of this chapter. The right side shows the movie clip centered as it is for the final example.

At the last step, the event listener is removed completely.

The great thing about this class is that it works just as well when the card is being turned back face down, going to frame 1.

Look at MatchingGameObject10.as and see where all the gotoAndStop calls have been replaced with startFlip. By doing this, we are not only creating a flip animation, but we are also giving the Card class more control over itself. Ideally, you might want to give cards complete control over themselves by having the Card10.as class more functions, such as those that set the location of the cards at the start of the game.

Limited Card-Viewing Time

Another nice touch to this game is to automatically turn over pairs of mismatched cards after the player has had enough time to look at them. For instance, the player chooses two cards. They don't match, so they remain face up for the player to inspect. After two seconds, however, the cards turn over, even if the player hasn't begun to select another pair.

To accomplish this, we'll use a Timer. A Timer will make adding this feature relatively easy. To start, we'll need to import the Timer class into our main class:

import flash.utils.Timer;

Next, we create a timer variable at the start of the class:

private var flipBackTimer:Timer;

Later on in the clickCard function, we add some code right after the player has chosen the second card, not made a match, and his or her score has been decreased. This Timer code will set up the new timer, which will simply call a function when two seconds have gone by:

flipBackTimer = new Timer(2000,1);
flipBackTimer.addEventListener(TimerEvent.TIMER_COMPLETE,returnCards);
flipBackTimer.start();

The TimerEvent.TIMER_COMPLETE event is triggered when a timer is done. Typically, a Timer runs a certain number of times, triggering a TimerEvent.TIMER each time. Then, on the last event, it also triggers the TimerEvent.TIMER_COMPLETE. Because we only want to trigger a single event at some point in the future, we just set the number of Timer events to one, and then look for TimerEvent.TIMER_COMPLETE.

When two seconds go by, the returnCards function is called. This is a new function that works just like the later part of the old clickCard function. It flips both the first and second selections back to the face-down state, and then sets the firstCard and secondCard values to null. It also removed the listener:

public function returnCards(event:TimerEvent) {
    firstCard.startFlip(1);
    secondCard.startFlip(1);
    firstCard = null;
    secondCard = null;
    flipBackTimer.removeEventListener(TimerEvent.TIMER_COMPLETE,returnCards);
 }

The returnCards function duplicates code that was in clickCard before, so in MatchingGameObject10.as I've replaced this duplicate code in clickCard with a simple call to returnCards. This way, we only have one spot in our code that returns a pair of cards to the face-down state.

Because returnCards demands a single event parameter, we need to pass that parameter into returnCards whether we have something to pass or not. So, the call inside clickCard simply passes a null:

returnCards(null);

Now if you run the movie and flip two cards, then wait, the cards will flip back on their own.

Because we have a removeEventListener command in the returnCards function, the listener is removed even if the returnCards function is triggered by the player turning over another card. Otherwise, the player would turn over a new card, the first two cards would turn back, and then the event would be triggered after two seconds regardless of the fact that the original two cards are already face down.

Sound Effects

No game is truly complete without sound. ActionScript 3.0 makes adding sound relatively easy, although there are quite a few steps involved.

The first step is to import your sounds. I've created three sounds and want to bring them each into the library:

  • FirstCardSound.aiff
  • MissSound.aiff
  • MatchSound.aiff

After we have imported them, they need to have properties changed. Name them all after their filenames, but minus the .aiff. Also, check the Export for ActionScript option and give them the same class name as symbol name. Figure 3.17 shows one of the sound's Properties dialog box.

Figure 3.17

Figure 3.17 Each sound is a class and can be accessed in ActionScript by its class name.

Next, we set up the main game class to play the sounds at the right time. First, we need to import two new classes so that we can use sound:

import flash.media.Sound;
import flash.media.SoundChannel;

Then, we create class variables to hold references to these sounds:

var theFirstCardSound:FirstCardSound = new FirstCardSound();
var theMissSound:MissSound = new MissSound();
var theMatchSound:MatchSound = new MatchSound();

I like to pass all sound playback through a single function. Let's call it playSound and add it to the end of the class:

public function playSound(soundObject:Object) {
    var channel:SoundChannel = soundObject.play();
}

Now, when we want a sound to play, we just call playSound with the sound variable we want to use, as follows:

playSound(theFirstCardSound);

In MatchingGameObject10.as, I've added playSound(theFirstCardSound) when the first card is clicked, and when a card is clicked while two mismatched cards are already showing. I've added playSound(theMissSound) when the second card is turned over and there is no match. I've added playSound(theMatchSound) when the second card is turned over and a match is found.

This is all that it takes to add sound effects to the game.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020