1. Modes
1.1. Multiplayer
1.1.1. LAN
1.1.2. Mouse and keyboard/ Xbox controller
1.1.2.1. Co-op
1.1.2.1.1. Harder than single player
1.1.2.1.2. More enemies
1.1.2.1.3. Sub-modes
1.1.2.1.4. Separate upgrades
1.1.2.1.5. Same screen
1.1.2.2. 4 player
1.1.2.3. Versus (Score based)
1.1.2.3.1. Split screen
1.1.2.3.2. Spread over multiple levels
1.1.2.4. Versus
1.1.2.4.1. One player sends enemy ships to kill the other player
1.1.3. Keyboard only
1.1.3.1. Co-op
1.1.3.1.1. Asynchronous
1.1.3.2. 2 player
1.2. Single player
1.2.1. Levels mode
1.2.2. Infinite mode
1.2.2.1. Hiscores
1.2.2.2. Enemies get progressively harder
2. Enemies
2.1. Ai types
2.1.1. Attack type
2.1.1.1. Aiming
2.1.1.1.1. Aims weapons toward the player
2.1.1.2. Directional shooting
2.1.1.2.1. Only fires in one direction
2.1.1.3. Multi-directional shooting
2.1.1.3.1. Fires in multiple directions at once
2.1.1.4. Collision
2.1.1.4.1. Trys to ram the player
2.1.1.4.2. Explodes on impact
2.1.1.4.3. Knockback
2.1.1.5. Support
2.1.1.5.1. Heals
2.1.1.5.2. Increases damage
2.1.1.5.3. Increases defences
2.1.1.6. Tracking
2.1.1.6.1. Fires projectiles that track the player
2.1.2. Movement type
2.1.2.1. Evasive
2.1.2.1.1. Trys to dodge player shots
2.1.2.2. Group
2.1.2.2.1. Trys to group with other enemies
2.1.2.3. Defensive
2.1.2.3.1. Surrounds and protects a bigger enemy
3. Player mechanics
3.1. Customisation
3.1.1. Weapon choices
3.1.1.1. 2 Weapons for most ships
3.1.1.1.1. Control
3.1.1.2. More than 2 weapons for some ships
3.1.1.2.1. Fixed weapons only past first two
3.1.1.2.2. Control
3.1.1.3. Types
3.1.1.3.1. Fixed
3.1.1.3.2. Energy
3.1.1.3.3. Projectile
3.1.1.3.4. Missile
3.1.1.3.5. Other
3.1.2. Ship choices
3.1.2.1. Different amount of weapon slots
3.1.2.1.1. 2 as standard
3.1.2.2. Different stats
3.1.2.2.1. Hull
3.1.2.2.2. Bonus damage
3.1.2.2.3. Stealth
3.1.2.2.4. Shields
3.1.2.2.5. Armor
3.1.2.2.6. Speed
3.1.3. Upgrades
3.1.3.1. Ships
3.1.3.1.1. One or more unique upgrade per ship
3.1.3.1.2. Hull
3.1.3.1.3. Shields
3.1.3.1.4. Armour
3.1.3.1.5. Base weapon damage
3.1.3.1.6. Stealth
3.1.3.1.7. Speed
3.1.3.1.8. Weapon type damage increases
3.1.3.2. Weapons
3.1.3.2.1. Damage
3.1.3.2.2. Rate of fire
3.1.3.2.3. Amount of projectiles per shot
3.1.3.2.4. Piercing
3.1.3.2.5. One or more unique upgrade per weapon
3.1.3.2.6. Armour piercing
3.1.3.2.7. Shield piercing
3.2. Progression
3.2.1. Achievements
3.2.1.1. Rewards ships and weapons
3.2.2. Hiscores
3.2.2.1. Online scoreboard
3.2.3. Unlocks
3.2.3.1. Ships
3.2.3.1.1. Side-grades
3.2.3.2. Weapons
3.2.3.2.1. Side-grades
3.2.4. Levels
3.2.4.1. Get Exp in all modes
3.2.4.2. Persistent over single player all modes
3.2.4.3. Bound to ships
3.2.4.4. Used for upgrades
3.3. Currency
3.3.1. Global
3.3.1.1. Used to unlock ships/weapons
3.3.1.2. Gained in all modes
3.3.1.3. Bound to save file