Prisoner's Dilemma
The Trap
Two players, one grid, and the same quiet question behind every number: what do you think the other is about to do?
Step 1 · Choose the game
Four classic setups — pick one, then make it yours.
Step 2 · Set the payoffs
Fine-tune (optional)
Realism — loss aversion
Negative payoffs are re-weighted before the engine solves — the grid stays as you typed it, and the marks follow the slider.
Step 3 · Read the marks
Step by step
Dominance elimination
Strategies that are never a best choice get stripped away, one round at a time.
- 1.Prisoner A's strategy “Cooperate” is strictly dominated by “Defect”.
- 2.Prisoner B's strategy “Cooperate” is strictly dominated by “Defect”.
Corner cases
Pure equilibria
Cells where neither player can do better by switching alone.
In between
Mixed equilibria
Probability mixes where each player is indifferent across their support.
No non-degenerate mixed equilibrium.
Step 4 · Play it out
Play a round
You are Prisoner A. Pick a row — the engine plays Prisoner B.
Pick a row above to play the first round.
You 0 · Engine 0 · 0 rounds
Step 4 · Play it out
Simulate 50 plays
Sample the selected equilibrium fifty times and watch the outcomes pile up.
This is a model, not a prophecy. Humans deviate from equilibrium — that's the most interesting part.