Knife Edge - Nose Gunner - Platform: Nintendo64

Expert mode
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Hold L + R +C-Up, then press C-Right, C-Left, B at the Kemco logo. 
A "Super Hard" difficulty setting may now be selected. 

Level select
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Select "Story" or "Team" mode, then hold 
C-Left + C-Right + C-Up + C-Down + R and 
press Right, Up, Left, Down when the level number is displayed. 

Tougher Difficulty
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Tougher Difficulty = As the Kemco logo qppears on-screen, 
hold R+L+C-Up, then press C-Right,C-Left, and B