(press the keys in the given order, in the main menu. if nothing happens try again)
Unlock all upgrades:
Up + Circle + Down + Right + Right Triangle + Left + Up
Unlock level 1:
Up + Up + Down + Down + Circle + Left + Triangle + Left
Unlock level 2:
Down + Down + Up + Up Circle + Right + Right + RIght
Unlock level 3:
Circle + Circle + Triangle + Up + Right + Square + Triangle + Left
Unlock level 4:
Right + Up + Right + Circle + Right + Left + Left + Triangle
Unlock level 5:
Circle + Left + Square + Right + Up + Down + Up + Square
Unbeatable mode:
Right + Circle + Left + Left + Square + Square + Down + Up
White backgrounds:
Left + Right + Square + Circle + Up + Down + Up + Square