Points earned in a single run unlock permanent rewards like new ship types, though points themselves reset after each run.
The game is set in a post-apocalyptic future where global warming has forced humanity into three massive underwater cities. Those who are not allowed inside these cities are banished to the hostile surface. You play as a "Robin Hood" figure, piloting a Swordship to steal vital supplies from the megacities and deliver them to the banished.
Players must collect supply crates during a run. These crates can either be used as one-time bombs to clear the screen or delivered at the end of a level to earn: High scores and leaderboard rankings. Extra lives. Random buffs and ship upgrades.
Unlike traditional "shmups," your ship has no weapons. You must position yourself so that enemy projectiles or line-of-sight attacks hit other enemy units.