Advance Wars is a turn-based strategy, which despite its pathetic name is a very good and complex game. With over 200 missions this game this game will keep you going for hours on end. To start off with you have 3 game modes, but when you complete training mode 3 more are unlocked and when you complete your first mission another is unlocked. Combine this with the ability to create your own maps and play multiplayer on 1 cart and 1 Game Boy you have a game which will last you for ever.
Complete Field Training Mode to unlock War Room, Campaign, Design maps and Stats. Then complete the first mission in Campaign to unlock the shop.