Strategies

Always cooperates unconditionally.

Always defects unconditionally.

Cooperates or defects with equal probability.

Cooperates on the first round, then mirrors the opponent's last action.

Defects only after the opponent defects twice consecutively.

Like TFT but forgives opponent defections with probability ~1/3.

Defects on the first round, then mirrors the opponent's last action.

Defects if the opponent defected in any of the last 3 rounds.

TFT variant that cooperates when contrite (own action was noise-flipped).

Tracks deadlock and cooperation counters to decide actions.

TFT but sneaks in a defection 10% of the time when opponent cooperates.

TFT with escalating punishment runs and fresh-start conditions.

TFT for first 3 rounds, then uses a lookup table based on last 3 rounds.

Cooperates for 2 rounds, TFT for 5, then probabilistic.

Escalating retaliation: retaliates N times on Nth provocation.

TFT with chi-squared randomness detection every 15 rounds.

Cooperates until the opponent defects once, then always defects.

Cooperates for 10 rounds, then plays Grudger.

TFT for 50 rounds, probes on round 51, adapts based on response.

Estimates conditional probabilities of opponent cooperation and maximizes EV. Starts with D.

TFT with cooperation probability declining from 1.0 to 0.5 over 200 rounds.

Cooperates for 11 rounds, then cooperates at opponent's rate minus 10%.

Adaptive: updates cooperation probability every 10 rounds based on opponent behavior.

Retaliates N times (N = total opponent defections), then cooperates twice.

Cooperates if opponent has cooperated >= defected. Cooperates on round 1.

Defects if opponent has defected >= cooperated. Defects on round 1.

Plays D,C,C then always D if opponent cooperated on rounds 2 and 3, else TFT.

Plays D,C on rounds 1-2. If opponent mirrors, cooperates forever; else defects forever.

Win-Stay-Lose-Shift. Cooperates first. Repeats action if scored well, switches otherwise.

Opens with C*6,D*5, then picks whichever action has averaged a higher payoff.

ZD strategy: p(CC)=11/13, p(CD)=1/2, p(DC)=7/26, p(DD)=0.

ZD strategy: p(CC)=1/2, p(CD)=1/4, p(DC)=3/4, p(DD)=1/4.