Lifeline is a territorial strategy game for two players (Black and White) that is played on the cells of an initially empty hexhex board. The recommended board sizes are between 3 and 12 cells per side.

A group is an entire set of connected stones of the same color. A single stone, not connected to others of its color, is also a group.

A group is dead if there is no path of connected empty cells between that group and any other of its color.

On your turn, perform the following actions in the stated order:
  1. Place a stone of your color on an empty cell.
    If it is your first turn of the game, perform this action twice.
  2. Remove all dead enemy groups.
  3. Remove all dead friendly groups.
(Note: the MindSports app performs all removals automatically.)

The board positions at the start and at the end of your turn must be different.

The last player to make a placement wins. Note that, after your first turn, you will always have a placement available unless you have no groups on the board.

To make the game fair, White will have the option, on their first turn only, to swap sides with Black instead of making a regular move.
(Note: the MindSports app swaps positions rather than sides.)