Essential features:

 Ã Splash screen/Menu
 Ã Cockpit/status displays
 Ã Limited rockets
 Ã Limited health
 Ã Non-zero enemy health
 Ã Terrain
 Ã Better enemy AI
 Ã Remove pitch auto-adjust
 Ã More enemies
 Ã Worlds/levels
 Ã Better collision detection
 Ã Sound
 Ã Name
 Ã Weapons start at ship's speed
 Ã Rocket targeting
 - Enemy models
 Ã Gameplay goals
 Ã Death animation
 - Level bosses
 Ã Fix Target model
 Ã Draw models in Display lists
 Ã Sound checkbox in settings
 Ã Levels
 Ã Win game screen


Bugs:

 ? Bad performance on GeForce 4 MX (!!)
 - InBounds bouncing
 Ã Death when being shot at bug
 - Line decals/polygon offset
   The disappearing speed booster


Nonessential features:

 Ã Preferences
   Ã No filled surfaces
   Ã Keyboard config
   Ã Fullscreen resolution
   Ã Start up in full screen mode
 Ã Particle trail for rockets
 - Music
 Ã Model caching
 Ã Redo letters
 - Story
 Ã Turrets
 - Scores
 - Mouse look
 - Radar
 Ã Camera shake
 - Fix motion blur
 Ã Gun powerups
 Ã Powerups carry over between levels, reset on death
 - Different colors for different levels
 - Level messages
 Ã Powerups displayed in console
 - More objects


Gameplay ideas:

 Ã Enemies drop pickups (health bonuses, rockets)
 - More weapons (bombs, mines, super missiles...)