Levels 2, 3, 4, 5, and 7 contain a bonus stage. These require that some sort of condition be met and are entered by flying into a hidden area.
Condition: None. Fly into the first ship opening along the bottom of the screen. It is located in the last section of the stage (after the giant carbonated bubbles) before meeting the Boss
Condition: Destroy all of the guns on the ground. Fly close to the low rock ceiling toward the end of the level and immediately before the last 'mountain'.
Condition: No power-up boxes at the bottom of the screen may be lit. Fly into the back of the Moai head located in the middle of upright three heads toward the end of the level. This particular head will be facing away from you.
Condition: Unknown. Fly through the fire at the corner of the inverted volcano. It is located just before the small passage that leads to the two-headed fire dragon.
Condition: Unknown. Fly through low corner just after the four turrets. Your ship would normally have to fly upwards diagonally at this point. Note: Collecting a lot of power-up modules by destroying turrets allows entry into the secret level area. The weapons select bar was on an empty box each time - missiles then lasers.
Enter the option menu from the title screen. Highlight the 'Game Level' selection and rapidly tap A until the 'Game Level' text changes to 'Arcade'. Press Start(2), to begin an arcade mode game.
Hold A button at the title screen. The demonstration mode will continue until reaching the Boss.
Rapidly tap X at the title screen until the total number of credits approaches eight. Press Start to begin the game before the title screen disappears.
Select the 'R Option' (rotating options) selection from the weapons panel. Obtain all four Options, then collect enough power-ups to highlight the 'Option' selection again at the bottom of the screen. Hold A to increase the radius of the R Options.
Press Start to pause game play, then press Up(2), Down(2), L, R, L, R, B, A. Press Start to resume game play. Your ship will gain missiles, force field, all options, and more speed. Note: This code may only be used once per level.
Select a game mode from the option screen, then press Start to enter the weapon selection screen. Press R to enter the edit mode. Press X, Y, X(2), Y(2), X, Y for a random selection.
Press Start to pause game play, then press Up(2), Down(2), Left, Right, Left, Right, B, A, Start.
Note: This trick requires a controller with a auto-fire feature. Put the L, X, and Y buttons on auto-fire at the screen with the 'Options', '1 Player', and '2 Player' selections. If done correctly, the number of credits should increase from 4 to 9.
Hold Left and press A(3) at the title screen. Then, press Start to begin game play.