A different labyrinth of rooms at each of the 18 levels of
Grail Castle requires a high degree of sustained concentration
for Parsifal the bewitched mushroom, whose quest is to seek
the Holy Grail and thereby transform back to human shape.
If in your fungoid role you can outrun or kill the various
monsters, the next step is to find and carry three coloured keys
to their correspondingly coloured rooms before moving to the next
level.
At each level you are given less time to achieve your task.
But if you fail, you are cast back down to level one (unless you
know the password) - a frustration heightened by the slow response
of the keyboard/joystick.