When on test-play while making or editing a game, you can hold Circle to temporarily disable random encounters while moving.
Edit Demo Game
Select the 'Edit Game' option at the main menu, then select 'File' then 'Load'. Your saved game files will appear. Press Circle, Up to highlight your memory card in the small box. Press X, then select the 'Sample' option. Select the 'Fu-Ma' sample game then enter Circle, X, Up, Left, Down, Right, Square, Triangle as a password. You can now edit the Fu-Ma demo game.
Editing Tools
When on test-play while making or editing a game, you can press Square to get as much money as desired, always win battles, or get any item.
Play A Full Game
Select 'Play Game' at the title screen. On the next screen, select 'Fuma' to play a pre-made game from the developers of Dragon Warrior. It cannot be edited as it is password protected.