satisfying the three conditions for n=2 and n=3 PG game. • We can realize mutual cooperation without a risk of being exploited. Efficiency ⌦ ⌦ ⌦ cooperation Defensibility ⌦ Distinguishability > ⌦ AllC AllC social dilemma can be solved by well-engineered strategies, not by appealing to our moral. Y. Murase, S.K. Baek, J. Theor. Biol. 449 p94 (2018)