The game is based on an old Windows solitaire game called
‘Midnight Sunitaire’. There are four difficulties, ‘easy’,
‘medium’, ‘hard’ and ‘extreme’, with easy being the default.

For the ‘hard’ difficulty, the game seems to be identical to the
solitaire game Geoffrey. The ‘extreme’ difficulty is usually
not solvable – and doesn’t really involve much strategy
(but the others do).

The rules are: A card (perhaps with other cards on top of it) can
be moved to a card if it is 1) face up, 2) of the same suit as
the destination card and 3) one lower in value. For example, you
can put a 5 of hearts on a 6 of hearts. The suits and values on top
of the card you’re moving don’t matter. Only kings can be placed
on empty piles. The goal is to build up ascending ‘real families’
on the four foundation piles.

A solver is not implemented.