In Neutron Star the player controls a spaceship trying to defend a system of satellites from being hit by planet fragments cast by an explosion.

The boulders must be collected by placing them in transport platform in front of the ship. Once the boulder is coupled, the player must move the ship toward a neutron star in the left edge of the screen. The neutron star exerts a magnetic force which will draw the ship into it. The ship must be moved carefully as it displays momentum. If the ship is drawn by the neutron star, it will be destroyed. Once close enough, the boulder can be released (by pressing the action button) and it will be drawn into the neutron star. The boulders can also be destroyed with rockets launched by the ship, but they are only available while the ship is not carrying any boulders.

As the game progresses, more boulders will appear at the same time. The color of the boulders change as they increase in number: one boulder will be red, 2 will be yellow, 3 will be green, 4 will be blue and 5 will be purple.

There are 16 satellites to be protected. If a boulder hits one of them, it will be destroyed. When 12 or more of them are destroyed, the magnetic power of the neutron star increases. The game is over when only 2 satellites are left.

The game has 4 skill levels. Levels 1 and 2 have respectively slow and fast boulders. Levels 3 and 4 have respectively slow and fast boulders also, but the satellites will be destroyed for at a time.