The aim of the game is to stop alien spacecraft from reaching the outer edges of a web-shaped cone (a type of wormhole maybe?).  You are able to patrol around the wormhole and need to use quick reactions and timing to shoot down the enemy spaceships.  If one of the enemy ships does manage to get to the outer edge of the wormhole, they'll be able to travel around the edge to capture your spaceship.  There are only two ways to avoid being captured if an enemy does reach the outer rim of the wormhole.  You can use a technique of jumping away from the wormhole and attacking from the distant position before you fall back toward the outer edge.  Alternatively you can use a megablast to destroy all enemy ships in view.  However, you only have one megablast per level and only a set number of jumps per level, so use these options wisely.

There are multiple levels to this game, and you will earn bonus points at the end of each level depending on how many jumps you have unused, and whether you have used your megablast capability.