After selecting 1p Stadium from the map, if this is your first time playing, you get to create your name and all your stats will be saved to the cart. In fact, there are 7 slots for you and 6 of your friends. And there's also a Guest slot if you just want to play without saving.

After selecting your name, you will be prompted which difficulty you want.

At first there are only 3 settings: Easy, Normal, and Hard.

After defeating Hard however, in the credits they will show you this cheat that will open up V-Hard (Very Hard)... And trust me, it is VERY hard.

Cheat: On the game settings screen of 1p Stadium, Hold the Z Button and Push L Button, L Button, A Button, B Button on Controller 1.

In 1p Stadium you are the character Ash. In this mode you challenge other characters from the Anime to a Puzzle League match.

If you select Easy you start with fighting Gary, then Brock, Misty, Lt. Surge, Erika, Koga, Sabrina, Blaine, Tracey, Team Rocket, and then finally Giovanni. The Gym Leaders will give you their Gym Badge if you defeat them.

If you select Medium you fight the above, but then you get to go on and fight the Elite Puzzle League players: Ritchie, Lorelei, and Bruno.

If you select Hard you fight the above, and then the Puzzle League Champion. Who else could that be but Gary!

If you select Very Hard, you fight everyone mentioned. And then you get to battle Mewtwo!