Symple (An abstract strategy game for 2 players)
Notes:
Adjacency in this game is orthogonal (not diagonal).
Term definition: "Chain" - A number of pieces of the same color which are adjacent to each other.
Each player has a set of pieces to use, one set black and one white.
The game is played on a square board which starts empty.
The game ends when the board is full. Each player's score is the number of their pieces on
the board minus X points for each chain of their color. The player with the higher score wins.
Before starting the game, the players must agree on a value for X.
Suggestions: 9 x 9 board: X = 4 / 13 x 13 board: X = 6 / 19 x 19 board: X = 10
(Note that on a board with an odd number of squares, an even X value prevents ties.)
White goes first.
On their turn, a player must take one of the following two actions:
"Plant" - Place one of their pieces on an empty space not adjacent to any of
their own pieces (in other words, they create a new chain for themselves).
"Grow" - Add one piece to each of their own chains, if possible (that is, for each chain,
place a piece on an empty space adjacent to at least one piece in that chain).
Note: If growing chain A causes it to join with chain B, chain B does not grow (so if it is
desired that chain B grow, simply grow chain B before growing chain A and joining them).
Exception to the Grow-or-Plant rule:
As long as neither player has Grown yet, Black may first Grow and then Plant in a single turn.
(Note that a grid-board can be used as if it were a size larger than
it actually is by playing on its intersections rather than its squares.)
If you like this sort of thing, you might enjoy this article:
https://www.abstractgames.org/symple.html