The key to strategy is staying alive. You get a new Smart Bomb and a new Ship every 10,000 points. As the game progresses, more aggressive enemies enter the playing area. To stay alive past 30,000 points, you'll need to know how to use each of the controls. The strategies below build on each other. It's essential to know the first strategy before you can move to the next, and so on. Once you get to the second strategy, you're still using what you've learned in the first one. You're simply adding to its depth. Remember: your basic objective is to kill all the Landers on the screen to complete an attack wave. It's necessary to kill them quickly, so that they don't mutate your Humanoids and Baiters don't appear.
These are certain basic strategies that must be developed and learned as soon as possible. All of these strategies, once learned, will continue throughout your entire game.
- Hit the Thrust and Fire buttons together. Consider these two buttons as one button. Always hit them together and hit them as fast as you can. Develop "Defender Fingers." Don't stop doing this unless you're in an instant-death situation. It's important to keep moving and to keep firing.
- Fly low. Many top Defender players seldom fly more than two inches above the Earth's surface. It's important in adequately protecting the Humanoids; it also tends to attract the aliens down level with your vehicle, this makes them easier to shoot.
- Kill kidnapping Landers. Destroy the Landers when they're raising your Humanoids to the top. Don't kill your Humanoids. Once you've killed a Lander, scoop up the Humanoid and return him to the Earth for extra points. You earn 500 points for saving a Humanoid, and an extra 500 for returning the Humanoid to Earth. You also get points for killing the Lander.
- Shoot several of your own humanoids. On levels after level 2, shoot most of your own humanoids early on in the level, keeping 1-3 to avoid the ground exploding. Guard the remaining ones jealously, and try to pick up one of them.Alternatively, on early levels if you pick up 9 or 10 humanoids simultaneously the game slows making baiters very killable! English defender aces called it "ten man pick up".
- Shoot at enemies before they can fire. Since they have to be on the main screen to fire at you, and since some of their shots are more or less impossible to avoid, use the radar to help you fire slightly before they appear to give them minimal chance to kill you.
Reverse strategy begins on the second screen. It should be used sparingly, and only when necessary. The most advantageous reverse strategy concerns the Mutants. Mutants are dangerous and difficult to kill. They also track your every move. A good way to kill them is to move up toward a Mutant, reverse and destroy it instantly. Your reversal will confuse the Mutant and stall him for an instant.
Hyperspace becomes necessary when the score starts building, at around 30,000 points. If you've dawdled during an attack wave, several Baiters may appear. These Baiters are faster moving and faster shooting than you are. There's no need to waste a valuable Smart Bomb on them. You might as well escape them with Hyperspace. Just beware: you have no idea where you'll end up. Be prepared to move instantly as soon as you've reappeared on the screen.
Smart Bomb strategy
Smart Bombs are valuable. Use them for maximum point potential. You should be able to survive without the Smart Bombs until around 30,000 points, at which point you'll have six of them. Wait until the pods appear on the screen at the start of the wave. Then use the Smart Bomb for over 1,000 points per pod and swarmers. The only other time to use the Smart Bomb is when you have no other choice. It's best to use the Smart Bomb smartly. Smart bombs do not necessarily blow up everything on the screen, but work most reliably when the player's ship is nearly stationary.
Pod and swarmer strategy
It's important for several reasons to try to break pods and kill swarmers fairly early on. Once they're dead the level becomes calmer and easier to play. In addition, baiters multiply when the number of aliens get down below 4; but swarmers are not counted towards that number and only make the level even harder at the end.
Swarmers can be passed fairly easily; if the player turns around immediately behind them, they will continue in the same direction, and can be shot from behind with impunity, they cannot fire backwards.
Swarmers will also collect along the players firing line if the player positions their ship in the middle of the screen. This also makes them much easier to kill.