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Defender for the TI-99/4A is a port of the 1981 Williams Electronics arcade game by the same name. The TI-99/4A version was published and distributed by Atarisoft on Solid State SoftwareTM Command Module cartridge. It was released during the fourth quarter of 1983. Defender's part number for the TI home computer system is RX 8506 and originally sold for $44.95 (USD).

Front of Retail Packaging for Defender for the TI-99/4A
Defender Retail Packaging [1]
Publisher(s) Atarisoft
Original Retail Price $44.95 (USD)
Programmer(s) unknown
Part# RX 8506
Format(s) Solid State SoftwareTM Command Module
Release 1983 (4th quarter)
Genre(s) Action, Shooter, Space


Defender is a two-dimensional side-scrolling shooter. It occurs on the surface of an unknown and unnamed planet. The player can move his/her ship left or right and up or down. The player's goal is to destroy as many alien invader's spaceships as possible and to prevent them from abducting the humanoids on the surface of the planet. When the player destroys all the enemies, he/she advances to the next level. The player loses a ship when it gets hit by enemy fire or if hyperspace jumps go wrong. The game ends when the player loses all his/her ships.

Advertising Blurbs

Back of Retail Packaging

The planet's fate is in your hands. Landers, Bombers, Baiters, Pods, and Swarmers. The alien attack has come, and defeat at the hands of crazed invaders threatens the humanoids. Their only hope is the spaceship, Defender. Armed with smart bombs and able to shift into hyperspace, Defender evens the score only to become the object of another foul attack: kidnapped humanoids transformed into killer mutants!

Triton Catalog - Fall 1985

The sophisticated Defender spaceship is your only hope against an alien attack that takes many forms. Armed with smart bombs and able to shift into hyperspace, Defender evens the score!

Fun Fact

The Arcade version of Defender appears in the book 1001 Video Games You Must Play Before You Die by general editor Tony Mott. [2]


Back of Defender Retail Packaging
Inserting the Cartridge
  1. Make sure alpha-lock key is in the UP position.
  2. Insert the Defender cartridge.
  3. Power on the TI Home Computer.
  4. Game Selection screen will appear.

Joystick Control

Plug the joystick into the joystick port. Using this one device, you can thrust, reverse, and change Defender's altitude - giving you unmatched freedom of the skies as you battle the invaders. Press the fire button to fire missiles.

Game Selection

The options for game selection are as follows:

  • One player, easy
  • One player, hard
  • Two players, easy
  • Two players, hard

Press + (plus) key to display options one at a time to make your selection.

Game Start: Press fire button on joystick #1 to start game.

Game Play Keys:, active during game play.

Restart: The + (plus) will end game and return to option screen.

Pause: The 'P' key is used to temporarily pause game play. Pressing 'P' again resumes game play.

Smart Bombs: The space bar is used to activate a smart bomb which destroys all aliens on the screen.

Hyperspace: Any other key causes the Defender ship to hyperspace to a random location somewhere in the playfield.

Game End

Upon complete destruction of player's Defender ships, the game end screen is displayed for five seconds. After which the game is displayed. During the game end screen the fire button can be pressed to cause the game option screen to appear immediately.


  1. Fly low. Good DEFENDER players seldom fly more than two inches above the planet, in order to protect their humanoids.
  2. Mutants are not as hard to destroy as it might appear. Thrust, then reverse direction and adjust your height simultaneously, and fire.
  3. Listen to the game sounds. Most of the time you'll hear a humanoid cry for help before you see it. Use the Scanner to find it. Try playing DEFENDER using the Scanner alone a few times to get a good idea of how it works.
  4. You can carry a humanoid around with you so that the aliens can never destroy all ten of them without destroying you. But if you touch the planet, the humanoid will immediately jump free.
  5. Use Smart Bombs only in extreme emergencies, or if there are enough aliens on the screen to push you past a 10,000 point mark.
  6. When you're thrusting, move up and down and fire continuously to sweep your area clean.
  7. Aliens become confused if you quickly reverse twice, giving you time to blast them.

The Scanner

Your view-screen shows your immediate area, but the Scanner at the top of the screen shows a much wider view. The area covered by your view-screen is bracketed in the center of the Scanner, so you can see what's happening to your right and left-a crucial factor with so many aliens around. By using your Scanner you can tell which kinds of aliens are where, and -more important - which of your humanoids are in danger. Humanoids and the different types of alien ships are distinguished by different colored blips.

Alien Ships

Each of the alien ships has a different function.

Landers, the first to appear, kidnap humanoids and fire white charges.

Bombers lay mines to trap you - you can't shoot mines, so you must avoid them.

Baiters appear if you take too long to finish off a wave - they move faster than Defender and fire white charges as they home in on him.

Mutants - transformed humanoids - are very dangerous. Once a humanoid is lost to you, spare no effort in trying to destroy it. They'll fly directly above or below you (where you can't hit them) and then charge.

The Pod is the most dangerous, because when it's destroyed it releases Swarmers. Swarmers track you closely, so zap them as quickly as you can.

All aliens except Landers can exit at the bottom of the screen and emerge from the top, or vice versa.

Rescuing Humanoids

You begin the game with ten humanoids. When a humanoid is kidnapped, it cries out for help. The Scanner is the fastest way to spot its position.

There are two ways of rescuing a humanoid: either destroy the Lander and let the humanoid fall back to the planet; or destroy the Lander, catch the falling humanoid, and carry it back to the planet. Letting the humanoid fall only works if it's low enough to fall safely. If the humanoid falls safely, you score 250 points, plus 150 points for destroying the Lander. If the humanoid dies, you score only the 150 points for the Lander.

Catching a humanoid in midair is more difficult and earns you more points. To catch a humanoid, shoot the Lander and maneuver Defender to touch the humanoid, then carry it to the planet. This earns you 1000 points, plus 150 for the Lander. If you catch the humanoid but don't return it safely, you still earn 500 points, plus 150 for the Lander.

If the Lander succeeds in carrying a humanoid to the top of the screen, the humanoid becomes a Mutant and returns to attack Defender. When all of the humanoids become mutants, or are destroyed, the planet explodes and vanishes. You continue to play and score points. With every fifth wave, a destroyed planet reappears and all ten humanoids are replaced.


Scores appear at the top of the screen. The score for Player 1, or a single player, is on the left; the score for Player 2 is on the right. How many lives and Smart Bombs Defender has left is displayed above the scores.

At the end of each of the first five waves, you score 100 bonus points for each surviving humanoid, multiplied by the number of the wave. At the end of each wave thereafter, you score 500 bonus points for each surviving humanoid. The wave number and the number of bonus points appear in the center of the screen. Any humanoid you're carrying returns to the planet.

  • Lander.png Lander . . . . . . . . . . 150

  • Mutant.png Mutant . . . . . . . . . . 150

  • Swarmer.png Swarmer . . . . . . . . . 200

  • Baiter.png Baiter . . . . . . . . . . 200

  • Bomber.png Bomber . . . . . . . . . . 250

  • Pod.png Pod . . . . . . . . . . . . 1000

Humanoid Rescue Mission

150 Points for each Lander plus:

Humanoid falls and lives . . . . . . . . . . . . . . . . . . . . . . 250 pts

Caught but not brought back . . . . . . . . . . . . . . . . . . . 500 pts

Caught and brought back . . . . . . . . . . . . . . . . . . . . 1000 pts



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