SDI: Strategic Defense Initiative is an arcade shoot 'em up developed and published by Sega in 1987.
In this game, you control the Strategic Defense Initiative satellite orbiting the Earth who must defend it from missiles and other antagonistic warheads sent by your enemy. Each stage is split into two phases, the Offensive Half and the Defensive Half. In the Offensive Half, it plays like a Horizontal Scrolling Shooter, where you destory the enemy's missiles by moving a crosshair (via trackball controller) and shooting at them while moving your own satellite (via joystick) to avoid projectiles shot against you. In the Defensive Half, it becomes a tower defense game like Missile Command, where you're tasked with projecting your base (presumably on the Moon); let the missiles damage your homeland too much and your game will prematurely reach game over.
SDI was ported to computer platforms published by Activision as well as the Sega Master System as Global Defense, as noted below. The arcade and the Sega Master System versions were re-released on PlayStation 2 in 2005 under Sega Ages 2500 Series label bundled with Quartet.
SDI: Strategic Defense Initiative contains examples of:
- All There in the Manual: There's no real plot in the game except a short opening in which a missile destroys New York City. You get that in the advertisement (with a tagline "The dreaded space war has at last begun!") but it's still an Excuse Plot at best. The manual for Global Defense just mentions that the "enemy" (whatever it is) is attacking Earth again, from bases all over the galaxy.
- Asteroid Thicket: The asteroid belt is one of the stages. It's full of space rocks, harmless as they're just background scenery save for those that have enemy bases on them firing at you.
- The Cameo: If you get a perfect rank in the Offensive Half, it plays a short animation featuring Flicky, the blue bird from Flicky.
- Gameplay Roulette: SDI shifts genres between the Offensive Half and the Defensive Half; the former is like a Horizontal Scrolling Shooter (although it's also a Vertical Scrolling Shooter because "enemies" can come from top and below, not just sides) and the latter is a defense game similar to Missile Command.
- Hold the Line: In the Defensive Half, your goal is to prevent missiles from hitting your base (Earth shows the North American continent as an exception), and keep the damage done to it to a minimum. When the Damage meter becomes full, it's a game over for you.
- Kill Sat: You play as one, which is remote-controlled and mounted with laser cannon, and that goes back to the cargo bay of a space shuttle when a stage ends. This is reflected in the controls, as you have to aim your crosshair with trackball and move the satellite with joystick.
- Market-Based Title: The Sega Master System version is re-titled Global Defense in the North America and Europe.
- Skippable Boss: Normally, you have to pass both Offensive Half and Defensive Half to complete a full stage. However, if you managed to shoot down every warhead in the first phase and get a perfect score, the Defensive Half is skipped.
- Standardized Space Views: Each stage has a background oriented in a way that you always see the Earth, the Moon, asteroids, the planet Saturn (in Global Defense), and Planet Spaceships at different angles that scroll past the screen. There is no shot of just the stars.
- A Winner Is You: The ending is non-existent; you have Statue of Liberty against black background, with white doves flying at least in Global Defense, and a couple lines congratulating you, and that's it. It also has a typo in spite of it.Congratuations [sic]You defended your state
