The droids eventually become sentient and, by way of revenge, start an attack against mankind, using a station to continually create more war machines.

Various power-ups, frequent in the first level, but progressively rare afterwards, permit an exponential increase of the spacecraft's seven different weapons (Guns, Buildup, Side Shots, Homing Missiles, Plasma, Magma, and Laserbeam).

When Team17 realized this, they released Project-X SE on Amiga CD32, a special edition with the difficulty toned down.

[1] A hack for the original game to enable the player to skip levels by holding down the fire button and pressing the escape key was also distributed on the coverdisks of several Amiga magazines.

According to Next Generation, Project-X was highly successful in Europe, but only sold in moderate numbers in the U.S.[2] Amiga Computing called it one of the best shooter games for that platform at the time, both for its technical excellence in graphics and sounds, and for its difficult and interesting gameplay.