Code-Zero

In the 21st century, Tokyo is attacked by an unidentified force. At first, it is thought to be a military coup d'état because all the weapons and personnel involved belonged to the forces of Earth, though investigations can uncover no motive from the participants nor connect them to each other. After ten more years of seemingly-random attacks on Earth cities by Earth forces, a researcher discovers the existence of an alien species which has been monitoring the planet and using telepathy to seize control of groups of humans in order invoke chaos. Soon thereafter, the aliens increase their assault by turning more of Earth's weapons on each other, seeking the planet's destruction. With few humans left able to act normally under the aliens' power, our protagonist climbs into an experimental ship, codenamed 'Zero', and departs in search of victory...

Code-Zero is a top-down sci-fi shoot-em-up. The player controls a spacecraft at the bottom of the screen and must evade enemy fire while simultaneously destroying enemy ships and tanks. Levels culminate in boss battles against a singular large enemy. Points are awarded for destroying enemy units and counted towards a high score. There are several upgrades which improve the ship's firepower as well as bonus items which award additional points when collected.