QUADREX

Players alternately drop one of their own stones onto any empty cell.
If this results in the formation of a small square with two similar
diagonal stones and one opposite stone, then the 4th cell is immediately
filled by the pair's color.  If this results in a similar situation,
the same applies again, and so on indefinitely.   One move equaliser.

The winner is whoever completes an orthogonal own-path in his direction.

Sample Game:

a b c d e f g h i j k l m n o p        Horz  Vert
. . . . . . . . . . . . . . . .   1.   l8    i8
. . . . . . . . . . . . . . . .   2.   i11   g10
. . , . . . . x . o o o . , . .   3.   h9    g8
. . . x . . o . . o x o . . . .   4.   g4    k6
. . . . , o . x x x x x . . . .   5.   l4    k4
. . . . o . x . o x x . . . . .   6.   j4    l5+
. . . . . o o o o o . . . . . .   7.   k3++  d4
. . . . . o x . x . . o . x . .   8.   e6    h5
. . . . . . . o . . . . . . . .   9.   f5    h3
. . . . . . x x x . . . . o . .  10.   h7    g6
. . . . . . x x o . . . . . . .  11.   f13   h12
. . . . , o o x . . . , . . . .  12.   h14   h13
. . . . . o x x o . . . . . . .  13.   h15   h16
. . , . . . x o o . . . . , . .  14.   g12   g11+
. . . . . . . o . . . . . . . .  15.   i13+  g14+-
. . . . . . . x . . . . . . . .  16.   f8    i10+
a b c d e f g h i j k l m n o p  17.   g7+   j6
                                 18.   i6 !  i5+
                                 19.   j7+   n8
                                 20.   n10   resign

This is a new connection game with lots of potential, using a novel mechanism to prevent the expected deadlocks of connections in orthogonal boards.