Your move.
Their response.
A different world.
Negotiate, compete, cooperate. Discover how your best decision depends on someone else’s—and how today’s advantage can reshape tomorrow.
Choose the tension you want to explore.
The trust dilemma
Two exporters can honor a quality agreement or cut corners. A private gain today can undermine tomorrow’s relationship.
Enter arena →02 / Price competitionRival firms
Choose a high, middle or low posted price while a rival chooses at the same time.
Enter arena →03 / Resources across timeThe shared river
Two communities withdraw from a renewable river. Today’s extraction changes the resource available next round.
Enter arena →04 / Free ridingBuild the flood barrier
Each community has 10 points and can contribute to a shared protection project.
Enter arena →05 / CoordinationChoose a common standard
Two firms need compatible systems but prefer different standards.
Enter arena →06 / Credible threatsThe costly standoff
Two fictional negotiators can yield or hold their position. Mutual escalation is costly.
Enter arena →07 / Offers and acceptanceDivide the project
You propose a share of a 100-point project. The counterpart privately commits to a minimum acceptable share before your offer is revealed.
Enter arena →08 / Private valuesSealed-bid auction
Bid for one license. Your value is 90 points. Your rival privately draws a value of 40, 70 or 100 each round.
Enter arena →Mission setup & sandbox
Changes apply when you start a new match. Save or export first if you want to keep the current run.
Advanced rules, reproducibility & custom payoffs
Noise replaces an intended action with a seeded random action, which can happen to be the same action. Future scores are weighted by discount factor raised to round minus one. Regeneration applies only to the shared river.
A repeated seed and identical actions reproduce a run. These are transparent teaching bots; seeds and local saves are inspectable, so hidden information is for learning, not secure competition.
Campaigns use original payoff tables and carry a chapter score record. Each chapter has its own economy; money and river stock do not transfer between different games.
Sealed-bid auction
Bid for one license. Your value is 90 points. Your rival privately draws a value of 40, 70 or 100 each round.
Read this arena’s rules before moving
First-price auction: the highest bid wins and pays its bid. Payoff is value minus payment; the loser gets zero. Ties split expected surplus equally, including a zero-bid tie. Your value of 90 is public; the rival knows its own draw. Bids are restricted to 0, 30 and 60.
Bidding below value trades off surplus if you win against the chance of winning. Post-round full-information tables are not Bayesian equilibrium solutions.
Discounted utility points · Mirror last action · Seed 31415 · Noise 0% · Discount 1
Your decision
The counterpart’s action is revealed after both choices. A round cannot be changed after resolution; replay creates a different path.
Resolve a round to see the score trajectory.
Save, export, compare or restore
Only clicking Save writes to this browser. Saved predictions can be read by other people using this browser profile. No game entries are uploaded. Save replaces the previous save; loading replaces your current session. An unfinished local round is not saved.
The learning is in the explanation.
Inspect the table, state what you believe the counterpart will do, and test one change at a time. The lab separates the outcome you observed from what a model predicts under specific assumptions. A winning score is a result to explain, not proof of a universally best strategy.
Connect competition to supply and demand → · Find more teaching resources →