Each player starts with a score of 501 and
takes turns throwing 3
darts.  The score for
each turn is deducted
from the total.  The
first player to reach
exactly zero, wins. The
last dart, however,
must land in a double
or the bull's-eye. 

Hitting the bull's-eye
scores 50. The outer
ring scores double,
and the inner ring
score triple of the
number indicated.