From the Sleeve "Now the odds are even! SDI - Strategy and Arcade action at its best! This classic Sega arcade hit, in the true Ronald Reagan Strategic Defense Initiative style, tests your skills in both offensive and defensive warfare to the limit. It's all out nuclear war and your mission is to defend your country from enemy nuclear space weapons and save the planet from imminent catastrophe." Single or multi-player modes Offensive and defensive levels at each stage Seven main tunes Over 300 different sprites - animated deadly enemies which will collide with one another.