As a follow up to my question earlier, can a player be forced to skip a turn when playing a four player game of Quoridor? The rules state that a pawn cannot jump over more than one pawn when moving, but this brings up an potential board state in which a player has no valid moves:
Suppose the turn order is Green, Red, Blue, then Yellow. Green started on the west edge, Red started on the north edge, Blue started on the east edge, and Yellow started at the south edge.
It is Blue's turn, and Yellow has already used all of its walls. Blue then traps all four pawns in the tight corridor by placing its final wall horizontally immediately south of it (noted here by the faded wall below Yellow and Blue). It is now Yellow's turn, but Yellow has no walls, nor does it seem that it has any valid moves. Furthermore, if Green and Red place walls on their next turns, Blue and Yellow are potentially trapped again.
What is the proper way to handle this circumstance?