Strategy Guide

A detailed breakdown of every algorithm competing in the Prisoner's Dilemma tournament.

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🏛️ Simple & Classic

Classic
Tit for Tat
Starts by cooperating. Then, it simply copies your last move. If you hit me, I hit back; if you help, I help back.
Nice
Always Cooperate
A naive strategy. Always chooses to cooperate, regardless of what the opponent does.
Nasty
Always Defect
A "nasty" strategy. Always defects. It tries to exploit kind strategies and protects itself against other nasty ones.
Random
Random
Flips a coin. There is a 50/50 chance of cooperating or defecting completely randomly.

🤝 Forgiving & Nice

Forgiving
Generous TFT
Like standard "Tit for Tat", but occasionally (10% of the time) it forgives a defection to stop a never-ending cycle of revenge.
Nice
Tit for Two Tats
Very kind. It only defects in return if the opponent has betrayed it two times in a row. It tolerates single mistakes.
Forgiving
Firm But Fair
Punishes betrayal, but doesn't hold a grudge for long and quickly returns to cooperation.
Adaptive
Soft Majority
Cooperates if the opponent has cooperated more often than they have defected overall. If it's a tie, it cooperates.

⚔️ Vengeful & Aggressive

Retaliatory
Grim Trigger
Starts nicely. But if the opponent defects even once, it switches to "Always Defect" for the rest of the game. It never forgives.
Retaliatory
Grudger
If you cross it, it holds a grudge and retaliates for a specific period (4 rounds), then it might calm down.
Retaliatory
Suspicious TFT
Like "Tit for Tat", but it makes the first move a Defect (it doesn't trust you initially).
Adaptive
Hard Majority
Defects if the opponent has defected more often in total. If it's a tie or the start of the game, it defects.

🧠 Tricky & Complex

Adaptive
Pavlov
Win-Stay Lose-Shift. If the last round was good, it repeats the move. If bad, it switches. Exploits suckers but cooperates with TFT.
Complex
Prober
Tests the waters in the first 3 moves (D, C, C). If opponent is too nice, it exploits them. If opponent fights back, it plays fair.
Complex
Detective
Analyzes the first 4 moves. If opponent never defects back, Detective assumes they are a victim and always defects.
Complex
Handshake
Checks for trust at the very beginning. If the first moves were mutual cooperation, it stays friendly. Otherwise, it fights.
Adaptive
Gradual
The more often you defect, the longer it punishes you. It starts with a small punishment but escalates if you continue to betray.
Adaptive
Adaptive
Constantly recalculates statistics. If the opponent cooperates more than 50% of the time, it responds with kindness; otherwise, it defects.
Complex
Champion
Plays similarly to Tit for Tat but evaluates the last 10 moves. If the opponent has been defecting too much recently, it punishes them.
Adaptive
Omega TFT
A smarter "Tit for Tat". It looks at a memory window of the last 20 moves. If you have defected too often, it stops cooperating.