The board is ordinary Life. Three live neighbours make a cell; two or three keep it alive. Patterns behave exactly as they always do — a newborn cell simply takes the colour held by the majority of its three parents.
Defection (optional) is the only added rule: a cell that survives while every one of its neighbours belongs to the enemy switches sides. It can never fire inside your own patterns, so gliders and guns stay intact until they touch enemy territory.
Each round both players place cells while the board is paused, then it runs for 30 generations. Twelve rounds, then the highest score wins. Who places first alternates.
Energy buys cells, one each. You earn a fixed income plus a share of your living population, so holding ground pays.
You may only build on empty cells near the ones you owned when your turn began — shown as a glow, and fixed for the turn, so you cannot crawl across the board. Your opening colony goes anywhere on your half, and if you are wiped out you get the half back to rebuild.
Score counts your living cells every generation, so lasting structures beat a last-second splurge.
The board wraps on every edge. There are no corners to hide in.