Start a new game - there are two difficulties to choose from - and pick a destination area on the map screen. Clear an area to unlock others.
Use the mouse to move the flying player robot LEFT and RIGHT. Click the LEFT mouse button to fire. Keep the LEFT mouse button pressed to charge up a powerful special shot and release the mouse button to fire. Press the ESC key during a level to pause the game and change options.
Each destroyed enemy releases a star. Quickly catch stars for combo points. Collect three stars and one of the enemies will carry a power-up item: shoot the enemy to release the power-up. Catch it to activate!
Barrier objects (planets, asteroids etc.) are handy for cover. But you can also shoot the barriers to release dark matter stars - grab these to fill up your energy meter.
Watch out for the alien UFOs that appear...