Extra credits: On continue screen, rotate D-pad clockwise to add up to 10 credits. I own 3 copies of this game. One tape requires counter-clockwise rotation. Even more extra credits: In sound test, play effect 62 three times, then exit sound test. Play game. On continue screen, rotate D-pad clockwise for up to 30 credits. Only 17 sounds appear on sound test, but if you hold button 2 and press Right you can access up to 95 sounds. Invincibility: Both controllers required. Hold down-right on controller 1 and hold up-left + button 1 on controller 2. Turn on system. Keep holding buttons until "R-TYPE" appears. Secret Level: On fourth level, enter the large block of mechanical cells at the top. There is two openings. Fly up into the first one and backwards into crescent. This last code I can't check myself since I never make it beyond the beginning of this level. All these codes work. I just can't test secret level code without invincibility code in use.