Cheats for Advance Wars (GBA)

New Play Modes
After beating all the field training missions, you unlock the War Room, Campaign, Design Maps, and Stats options.

Hard Mode
Hold select when choosing Campaign mode to play advanced mode.

New C.O.s
After beating the Campaign mode, you can purchase additional CO's.

Clear Data:
Hold L + Left directional button + Select while turning the GBA on.

In-Game Reset:
Press Start + Select + B + A while playing.