Zarathrusta is a cave-flying game influenced by Thrust. Apparently, the resistance forces have captured a number of space ships, which could aid in the struggle against the empire. However, these ships need fuel, and that fuel is find in the form of "klystron pods", which must be recovered from a range of hostile environments.
Your task is to fly your small spaceship above and below ground, capturing the pods. Your spaceship can rotate in 360 degrees, allowing for easy movements through the cave systems, if it wasn't for gravity pulling you down, and inertia, which means you could crash into walls or other objects if you don't turn around and thrust in the other direction.
Each level is cleared by recovering the klystron pods, which are the same thing as the ball you pick up in Thrust. Pick up the pod with your tractor beam, and a towing line will be attached. Towing the ball means that you have another object altering your course, though; if you break quickly, the forces of inertia will make the ball travel forward, pulling you in its direction. At later levels, the pod becomes heavier, and must be pulled using a force field. Travelling too fast will make the ball slip out of the field, forcing you to pick it up again, possibly from a very dangerous area.
The levels are guarded by cannons, which can be shot down using either your conventional cannon or a laser cannon. Beware, though, for the laser eats up your fuel supplies very quickly. Refueling is possible by activating the tractor beam above the fuel pods stationed throughout the levels.
Whereas Thrust used vector graphics, the visuals of Zarathrusta consist of bitmaps.