You can pilot one of three unique spaceships with different sizes and characteristics to fight your way through 30 levels of enemy ships. You can upgrade 6 different attributes which all affect combat.
Summary of commands:
Navigation: Arrow keys or WASD
Shoot: spacebar
Pause: ?P?. This will also show you your current statistics which are also shown at the end of the game.
Upgrade: ?0-6? depending on the specific upgrade. Use this when you have collected an upgrade token. Be warned that when you upgrade, you cannot shoot for a few moments until the upgrade completes.
0: Repair Armor
1: Energy
2. Energy Recharge Rate
3. Ship speed
4. Shield
5. Shot speed
6. Shot damage
When the frame around the icon for the resource becomes yellow, then it is maxed out and can not be upgraded anymore. Use ?T? to toggle your energy systems to route power more to shields or to weapons, depending on your needs. It starts with more power routed to shields. Once toggled, it can not be toggled again for a short while. You will know when you can toggle again when the frame around it becomes yellow.