AI and stuff...

Gradius, is one of the Sci-Fi games I like... Konami's games are the best for me, because their games are very detailed and excellent.

Some Gradius Factors You Missed:
-Upgrades Tab (in the order):
speed-up, missile, back-up shooter, laser, option(helpers in combat), ?(shield), !(special)
note: ! is found at Gradius 3
-Main menu(Duh)
-Stunt Awarding
example: going under hills without getting cornered or almost colliding with the edges of structers(not enemies)
-Turrets must aim before shooting
-Supply Facilities(those chamber-like thingies which spawns enemies)
-Statistics Tab(Duh)
Score, Lives(presented as a triangle thingy), Hi-Score
-Boss Expire Time(the time where boss self-destructs when the player is taking too long to defeat the boss)
note: my estimate is 30 minutes.