Here are some cheats and tips for the game Syd Valis.
Invincibility:
Press Up, Down, Left, Right, A,
B, Up, Down, Start at the title screen.
A sound will confirm correct code entry. Yuko will be wearing
a bikini when game play begins. Her energy will return to full
after it reaches zero.
No background music:
Press B + Start at the title screen. Note:
The music will be re-enabled if you lose a life.