Highlight "Options Mode", then press Down to highlight "Option: Cheat Codes" and press X. Then, enter one the following codes to adjust the difficulty level of the game:

howhardcanitbe0 (Easiest)
howhardcanitbe1
howhardcanitbe2
howhardcanitbe3
howhardcanitbe4
howhardcanitbe5
howhardcanitbe6
howhardcanitbe7
howhardcanitbe8
howhardcanitbe9 (Hardest)