Use Phaser (X key) to turn asteroids into rings.
Smaller asteroids turn to rings faster than bigger asteroids.
Torpedos (C key) break up asteroids.
Rings disappear after a short while.
Fly over rings to capture them.
Fly to catcher and eject rings into it.
You automatically warp to a new system when 'Rings Left' is 0.
Aliens will hassle you as you get deeper into their territory.
Capturing rings you money to buy upgrades for your ship, such as
Explosive thrust, shields, bombs, ring gravity, faster torpedoes, etc.