Home > Articles > Programming > Games

This chapter is from the book

Designing the Game

Now that you understand the basic idea behind the game, let's focus on a few details regarding the design of the game. The player's car can move horizontally across the game screen, which means that its position is confined to the x axis. The player can shoot up vertically—with his Twinkie missiles terminating at the top of the screen, similar to the missiles in the Meteor Defense game from Hour 19, "Example Game: Meteor Defense."

The aliens in Space Out can move around in any direction and at different velocities. The Blobbo and Jelly aliens bounce off of the edges of the screen, while Timmy is allowed to wrap around and appear on the other side. This is because Timmy has a tendency to fly horizontally across the screen, whereas the others move around a little more randomly. All the aliens fire missiles down toward the player's car—with the missiles terminating when they strike the car or the ground. The aliens are immune from their own missiles, so they can't hit each other. This is a good thing for the aliens because they aren't very careful in terms of how they aim.

Space Out has no discrete levels and no real goal other than surviving. However, the difficulty level of the game does gradually increase as the player progresses through the game. The difficulty of the game increases by adding new aliens at a faster pace. Eventually the player will have his hands full trying to contend with a never-ending army of aliens. That's the whole fun of shoot-em-ups!

To help you get a feel for how the Space Out game is laid out, take a look at Figure 21.1.

Figure 21.1Figure 21.1 The Space Out game consists of a starry background, a ground desert image, a car, aliens, and missiles that are fired between the car and aliens.

The figure shows the background image of the desert, which serves as a backdrop for the car to drive around on. The starry background still appears in the majority of the screen, whereas the background image shows the desert where the car drives around. The background image actually includes a horizontal band of sky that helps blend the desert landscape into the starry background. The car sprite moves around on top of the desert background image. The aliens appear in the sky and move around trying to hit the car by firing various missiles. Of course, the car also fires missiles back at the aliens. The score for the game is displayed in the upper right corner of the game screen, along with the number of remaining lives (cars).

Now that you understand the basics of the game, it's important to examine the sprites that it requires. Following is a list of the sprites that go into the Space Out game:

  • Car sprite

  • Alien sprites

  • Missile sprites (from the aliens and the car)

  • Explosion sprites

The only type of sprite in this list that I haven't mentioned is the explosion sprite, which is used to show an alien being destroyed by a missile, as well as the car being destroyed by an alien missile. Two different sizes of explosions are actually used in the Space Out game. The larger explosion is used to show an alien or the car being destroyed, whereas the smaller explosion is used to show a missile exploding. This distinction is important because it shows how missiles cause a smaller explosion when they simply crash into the desert, as opposed to hitting the car.

In addition to the sprites, the Space Out game requires several bitmaps. Following are the bitmap images required of the game:

  • Background desert image

  • Car image

  • Missile image (fired by car)

  • Alien images (Blobbo, Jelly, and Timmy; animated)

  • Missile images (fired by each of the three aliens)

  • Explosion images (animated; small and large)

  • Small car image

  • Game over image

These images flow directly from the design of the game that you've covered thus far, so there hopefully shouldn't be any big surprises here. Perhaps the main thing to point out is that the aliens all rely on animated images to provide them with a more interesting appearance as they move around on the game screen. The only other animated images in the game are the explosion images, which go with the explosion sprites.

The score needs to be maintained throughout the game, as well as the number of remaining lives (cars); the game ends when all three of your cars have been destroyed. The difficulty level of the game is stored away in a global variable, and gradually increases as the player racks up points and progresses through the game. Another important piece of information is the familiar Boolean variable that keeps track of whether the game is over.

The last global game variable required of Space Out is an input delay variable that helps add some restraint to the player's ability to fire missiles rapidly. Without this input delay variable, it would be too easy to wipe out the aliens by holding down the fire key (Spacebar) and raining missiles on the aliens with little effort. By slowing down the number of missiles that can be fired, the player is forced to be more accurate and evade aliens when they miss. Establishing the appropriate delay is somewhat of a trial-and-error process, and you might decide that the game is more fun with a slightly different value than I used.

To recap, the design of the Space Out game has led us to the following pieces of information that must be managed by the game:

  • The number of lives (cars) remaining

  • The score

  • The difficulty level

  • A Boolean game over variable

  • A delay variable for firing input

Before diving into the code for the Space Out game, you need to add a new feature to the game engine. Although the game engine is a flexible piece of software, you will likely find yourself adding new features in the future to accommodate the special needs of new games. This is a good thing because you get to reuse those features in any game that you create from then on.

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.


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.


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.


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.


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


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


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.


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.


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