You are the captain of a space ship and fly through missions to earn money. With the money you can buy parts to build your weapon in your space ship. You can also buy bigger and better ships which can fit more parts. Building a small weapon is straight forward, but later you can build extremely strong weapons if you use the available space wisely.
The game is an light-hearted version of an arcade space shooter but has substantial depth regarding the mechanics. If you like to tinker around and optimize stuff - This is the game for you.