Verge

Verge is a two-player strategy game played on an initially empty hexhex board. The players take turns placing a stone of their color on an empty hex. The first player unable to place a stone has won.

A partitioning group is a group separating two hexes outside the group, in the sense that all paths between the two hexes go through the group.
You're not allowed to place adjacent to a friendly partitioning group.
When a group becomes partitioning, remove all nonpartitioning groups adjacent to it.

The game is balanced with the pie rule: One player decides what player 1's first placement will be, and the other player decides whether to play as player 1 or player 2.

—description from the designer