Power Ups (Lasers, Missles, Options, Double Lasers)
While you are in the game pause the game and enter the following codes. (Note you may only enter 1 code per level. So if you play a level without using a code that means the next level you may enter 2 codes.)
In Gradius III, finish the game once or play for at least ten hours. Extra Edit will become available, allowing you to edit a weapon combination from all the weapons.
Extra Mode / Cube Attack
In Gradius III, complete up to level 8, and under the game's menu, Extra Mode will become available. This is basically a screen that lists all the game's extra features, as you accumulate them. The first Extra Mode item is ''Cube Attack.''
Gradius I Mini-Game in Gradius III
In Stage 10, when you are at the last boss of the game, get hit by the boss' attack that comes out of the mouth. You will then be taken to the first stage from Gradius 1. This mode will then be unlocked in ''Extra Mode''.
Gradius IV Stage Select
Complete the game without using one continue to unlock Stage Select in the main menu of Gradius IV.
More Extra Edit
After getting the first Extra Edit, beat the game again or have a total play time of at least 20 hours. Even more Extra Edit weapons will be available.
Salamander Mini-Game in Gradius III
In Stage 10, when you are at the last boss of the game, get hit by the boss' attack that comes out of the mouth. You will then be taken to the first stage from Salamander (AKA Life Force in NA for NES). This mode will then be unlocked in ''Extra Mode''.