To get four extra battle arenas press start as fast as you can at the Mode select screen. You will hear a chime letting you know when you did it right.
Bonus World:
To get to Rainbow Palace, you must find/achieve all 100 gold cards and beat the game.
Bonus Option:
Beat the Adventure Mode on Normal difficulty to get the Sound Test.
Bonus Option:
Beating the bonus world will open the credits option.
Bonus Option:
Get all the gold cards including the gold cards in the Rainbow Palace and then defeat Sirius.
Now
the Full Power option will be open. This gives you max number of bombs, max power bombs,
red
bombs and remote bombs.
