Shared jar
Your contributions grow. Everyone gets an equal share.
What will you choose?
Play together without signing up. See the rules in your language.
Your player
Quick join any game
Find a room across all games, or start a randomly chosen game.
Prisoner’s dilemma
A one-round temptation. A repeated relationship.
Statistics
Explore the games
Cooperation and shared risk
Renewable commons
Take a share. Leave enough for another round.
Players 3–6Stag hunt
Aim high together, or take a safer reward.
Players 2Volunteer’s dilemma
Someone has to pay for everyone to benefit.
Players 3–6Minimum effort
The lowest effort sets the shared outcome.
Players 3–6Collective risk
Reach a shared target while protecting what you keep.
Players 3–8Bank withdrawals
Withdraw now or wait for the remaining investment.
Players 3–8Upstream and downstream
Invest together, then take water in a visible order.
Players 3–6Distribution and bargaining
Ultimatum
Offer a split. Both get nothing if it is rejected.
Players 2Dictator game
The split is entirely up to one player.
Players 2Centipede
Take now, or pass a growing pot.
Players 2Coalition bargaining
Propose a complete split, then seek enough votes.
Players 3–7Nash demand
Ask for your share. Too much together leaves both with zero.
Players 2Shrinking-pie bargaining
Reject an offer to switch roles and shrink the pot.
Players 2Different preferences
Match the choice, even when you prefer different outcomes.
Players 211–20 requests
Ask for more, or aim one below your opponent.
Players 2Information and trust
Trust game
Send it, multiply it, and see what comes back.
Players 2Sender and receiver
Send a recommendation with private knowledge. Will the receiver follow it?
Players 2Inspection game
Choose whether to inspect, or whether to comply.
Players 2Information cascade
Weigh your private clue against earlier public guesses.
Players 4–10Auctions and strategy
Chicken
Hold your ground, or yield before a collision.
Players 2Traveler’s dilemma
Make a claim. The lower claim sets the payout.
Players 2War of attrition
Wait for the prize, but waiting has a cost.
Players 2Guess two thirds
Guess the target made by everyone’s guesses.
Players 3–10Minority game
Pick the side that fewer people choose.
Players 3–7Congestion routing
A route gets costly when too many take it.
Players 3–8Dollar auction
The winner and runner-up both pay their last bids.
Players 2–6Common-value auction
Bid using your private clue about one shared value.
Players 3–8Battlefield allocation
Allocate every token across battlefields with different rewards.
Players 2