SDI: Strategic Defense Initiative is a 1987 shoot-'em-up arcade game developed by Sega for the Sega System 16 arcade platform.
Gameplay
Unusual for its time, SDI has the player assume the role of a satellite, tasked with destroying enemy satellites and missiles. Each level is divided into two "modes" - "offensive" mode, which takes the form of a sidescrolling shoot-'em-up, and "defensive" mode which is built more similarly to Atari's Missile Command. Beating both modes allows the player to progress, however, if the player can destroy all the enemies in offensive mode, defensive mode does not take place.
SDI not only gives the player control over the movement of the satellite, but also its aim. This mechanic was implemented in the original arcade cabinet through the form of a joystick and trackball - the joystick moving the player, the trackball moving the crosshair. On the top of the joystick is a button for firing.
A perfect game of SDI will result in the satellite being replaced with Flicky.
Ports
SDI was ported to the Sega Master System in 1987/1988, where western versions were renamed Global Defense. The Master System version, as well as cutting back on the graphical and audio quality, has to vastly reduce the difficulty of the game to match up with a new control scheme - as the console lacks a trackball, the player needs to switch between moving and aiming during play (holding 
while moving the D-Pad allows the satellite to move, otherwise the D-Pad only controls the crosshair). This makes moving and aiming at the same time impossible. 
fires.
Activision brought the game to home computers in Europe - the Amiga, Amstrad CPC, Atari ST, Commodore 64 and ZX Spectrum (not to be confused with S.D.I., an unrelated game also released for the Amiga and Atari ST).
These days, SDI is often grouped with another arcade game from the era, Quartet. Both were released as part of Volume 21 of the Sega Ages 2500 series, SDI & Quartet for the PlayStation 2. SDI & Quartet: Original Soundtrack contains the official soundtrack of both games.
Production Credits
Arcade Version
Planed by: Black Holl Tomo
Project Leader: Joe Kacchan
Programer: Sweet Tohchan, Anatano Pideshi, Ippo Ogapi
Character Design: Saitama Kenji, 8940 Kon
Scene Design: Henchan
Music by: Funky Gerogero
Sound Effects: Nao Chan
Mechanical Engineer: MI.U.I.Hachi
Enemy Creation: Demon Taka
Data Adjust: Nanno Icchan
Special Thanks: Mina Inochi, Hakusyon Daimaohe, Mamiko Chan, Uso Happyaku
Special No Thanks: Ashidematoi People
Presented by: Sega, Chin_Chin Brothers
Physical Scans
Master System version
|
74
|
Sega Retro Average
|
| Based on 3 reviews
|
| Publication
|
Score
|
Source
|
| ACE
|
62
|
№14
|
| Computer & Video Games
|
80
|
№78
|
| The Games Machine (UK)
|
81
|
№5
|
|
| Master System, US
|
Cover
|
 Cart |
| Master System, EU
|
Cover
|
|
|
Master System, EU
"no limits" variant
|
Cover
|
|
|
Master System, EU
® variant
|
Cover
|
|
|
Amiga Version
Amstrad CPC Version
Atari ST Version
|
83
|
Sega Retro Average
|
| Based on 2 reviews
|
| Publication
|
Score
|
Source
|
| ACE
|
84
|
|
| Computer & Video Games
|
81
|
№86
|
|
Commodore 64 Version
|
63
|
Sega Retro Average
|
| Based on 2 reviews
|
| Publication
|
Score
|
Source
|
| Computer & Video Games
|
54
|
№116
|
| Computer & Video Games
|
72
|
№118
|
|
ZX Spectrum Version
|
59
|
Sega Retro Average
|
| Based on 1 review
|
| Publication
|
Score
|
Source
|
| Computer & Video Games
|
59
|
№116
|
|
| ZX Spectrum, EU
|
Cover
|
|
|
