Gradius

Codes

Acquire Speed Up, Missile, two Options, and Barrier

Pause the game, then press Up, Up, Down, Down, Left, Right, Left, Right, B, A, Start. This can be performed once, plus one more time for each time a Big Core boss is destroyed before its core turns red.

Continue

At the Game Over Screen, press Down, Up, B, A, B, A, B, A, B, A

Level warps

Accomplish the following tasks to warp to a new level.

Effect	Code
Warp to level 3 after defeating Core Fighter	In level 1, when the thousands digit of your score is even, destroy 4 hatches
Warp to level 4	Destroy Xaerous Core at end of level 2 within 2 seconds of its core turning blue
Warp to level 5 after beating level	Destroy 10 stone heads in level 3

Game Genie Codes

SXOOYYVI        Both players have infinite lives 

AENELZLA        Both players start with 1 life

IENELZLA        Both players start with 6 lives 

AENELZLE        Both players start with 9 lives

KOXOLYSP        Keep power capsules 

NNOEKPIE        Increase force field protection 

YGUONUZS        Never lose weapons
YGKPUUIL