DIAMOND & PIVOTS (v.2)

1. On each turn, each player passes or drops a stone on an empty cell.
   There is a swap option after the first half-turn.
2. If any diamond patterns with four friendly stones are made, the player
   must choose one, choose a stone from it (the pivot), and place
   its other three stones in a line starting from the pivot.
  2.1 Every stone (of either color) that was on those destination cells
      are captured and removed from the board.
  2.2 If, after a pivot movement, another diamond shape is made,
      the player must repeat this procedure.
3. A stone may not be played to make a group of more than four stones,
   unless it thereby makes a diamond.
4. After two consecutive passes, wins the player with more
   stones (if equal, wins the 2nd)

Sample game:
abcdefghijklmnopq
    . . . . .      1.  c7 <--pied  i5
   . . . . . .     2.  d6          j4
  . . . . x x .    3.  e7          k5
 . . o x o x . .   4.  h4          m5
. . x x . x o . .  5.  l4        j6,h4-n4::
 o o x o . . . .   6.  h6     k5,k5-e5,h4-e7:
  o x . . . . .    7.  f4          l4
   . . . . . .     8.  m5          k3
    . . . . .      9.  j4          m3
abcdefghijklmnopq 10.  b6

And then...

abcdefghijklmnopq
    . . . . .      1.  c7 <--pied  i5
   . . . . . .     2.  d6          j4
  . . . . x . .    3.  e7          k5
 . . o . x . . .   4.  h4          m5
. . . . x x x x .  5.  l4        j6,h4-n4::
 x x x x . . . .   6.  h6     k5,k5-e5,h4-e7:
  o x . . . . .    7.  f4          l4
   . . . . . .     8.  m5          k3
    . . . . .      9.  j4          m3
abcdefghijklmnopq 10.  b6

10...   l2,k3-h6::,h4k5,i5-o5:,e5i6,h6-b6::

First player resigns.