public static class GameOfLife {
        private int currentGen = 0;
        private int nextGen = 1;
        private Cell headCell; // populated somehow

        public void tick() {
            // visit entire graph
            // we won't make assumptions about the number of neighbours and will handle backtracking by storing the current generation on the cell
            tickCell(headCell);

            // now flip the generations
            // we could use booleans but this allows us to potentially store more historical generations
            int nextNextGen = currentGen;
            currentGen = nextGen;
            nextGen = nextNextGen;

        }

        private void tickCell(final Cell cell) {
            if (cell.currentGen == nextGen) return; // already visited

            // Move this cell to the next generation
            cell.currentGen = nextGen;

            // Visit all neighbours, counting live ones
            int liveCount = 0;
            for (var neighbour : cell.neighbours) {
                if (neighbour.genAlive[currentGen]) liveCount++;
                tickCell(neighbour);
            }

            // Determine this cell's new generation state
            // [deliberately verbose ifs for clarity]
            if (cell.genAlive[currentGen]) {
                if (liveCount < 2) cell.genAlive[nextGen] = false; // you underpopulated bro
                else if (liveCount < 4) cell.genAlive[nextGen] = true; // you ok bro
                else cell.genAlive[nextGen] = false; // you sexed too much bro
            } else {
                if (liveCount == 3) cell.genAlive[nextGen] = true; // you sexed back to life
            }
        }

        public static class Cell {
            private int currentGen = 0;
            private boolean[] genAlive; // populated somehow
            private List<Cell> neighbours; // populated somehow
        }
    }