  Tumbleweed is a popular two-player perfect-information new territorial game
played at the prestigious Mind Sport Olympiad. We define a generalized version
of the game, where the board size is arbitrary and so is the possible number of
neutral stones.
  Our result: the complexity of deciding for a given configuration which of the
players has a winning strategy is PSPACE-complete. The proof is by a log-space
reduction from a Boolean formula game of T.J. Schaefer, known to be
PSPACE-complete.
  We embed the non-planar Schaefer game within the planar Tumbleweed board
without using proper "bridges", that are impossible due to the board's
topology. Instead, our new technique uses a one-move tight race that forces the
players to move only according to the protocol of playing the embedded 4-CNF
game.
