In Pachinko one shoots a small metal ball into a forest of pins, then gravity then pulls it downwards so that it will either fall into a pocket (where you win a prize) or the sink at the bottom of the machine.  The spacing and distribution of the pins will help to insure that one only wins certain prizes with low probability.

Now imagine that we have a more general game where:

(1) - The ball is simply diffusing in 3-space (like a molecule undergoing Brownian motion).  I.e. there is no fixed downward trajectory due to gravity.  

(2) - You win a prize if the ball diffuses over a particular coordinate, just like one of the pockets in regular pachinko.

(3) - We generalize he pins as a set of impassible coordinates.

(4) - We define a 'sink' as an always accessible coordinate.

Given access the 3-space coordinates for (2), (3), & (4), what's the most efficient way to find whether the game is 'winnable', or if the ball will fall into the 'sink' with a probability of unity?