Top Gun: The Second Mission

Top Gun: The Second Mission is an NES game by Konami.

Title Screen Secrets
Hidden features accessed via the title screen through Game Genie codes and button combinations.

Stage Select / Invulnerability
The Game Genie codes (European version),  (American version), or  (Japanese version) re-enables options that are otherwise inaccessible.

Hold A or B and press Start on controller 1 to get invulnerability or stage select, respectively. Holding both, as you may expect, gets you both.

Congratulations Screen
In addition to the above effects, the European version adds another – hold A on controller 2 and press Start on controller 1 to change the Game Over screen to the Congratulations screen.

The screen appears normally in-game instead of the Game Over screen when you score at least 50,000 points.

Ending
Also exclusive to the European version – after enabling the Game Genie code, press A + B + Start on controller 1 to see the ending.

Build Dates
At the end of the ROM is an ID with the date that version of the game was compiled. A similar ID is found in many others Konami games, with some variations.

So the Japanese version was compiled on August 10, 1989; the American version on August 16; and the European prototype (M0.1) on June 17, 1991.