Press the [Enter] key during play, and an input field appears. 
Then input the following cheat codes:

Code                               Result
---------------------------------------------------------------------  
Icompletedthisghostgame          - Carries you into the unreal world.
IfIwantIgotit 32                 - Gives you items. The number at the 
                                   end is the number of the item you want.
Seethesilverlining               - Remove the darkness.
Showmetheworld                   - The whole card releases, and displays 
                                   also the positions of the opponents, 
                                   who disappear to darkness.
Thefierceunknownpower 99         - Increases Magic to 99
Thegreathealthpower 99           - Increases Health to 99
Thehealthyspiritpower 99         - Increases Brain to 99 
Theoriginaldexteritypower 99     - Increases Dexterity to 99 
Therealmusclepower 99            - Increases Strength to 99 
ThesoulHunter'sholyPower 10      - Increases power to 99 
Youcansaymoneyiseverything 10000 - Gives you bucks. 
Yougainasoneplease 30            - Gives weapons. The number at the end is 

The cheats are case sensitive, and must be entered exactly as shown.