You have received absurd testament with a really strange last will of your distant relative. He gives you a special spaceship with ability to travel in another dimension, and entrusts you the task to fight with secret Labarik race that exists there. You need to stay in combat as long as possible, take top hi-scores and compare your results with your friends.
Your main goal, according to testament, is to become a Legend. Upgrades will help you a lot with rank gaining. You can unlock different upgrades for taking different ranks, then you can switch them on and off in special menu at the title screen. The game also has entertaining and relaxing purposes, so enjoy your time.