Don't explain the prisoner's dilemma, measurement error, supply and demand, second-price auctions, Newton's third law, mixed strategies or tax incidence. Play it.
On their phone
Your choice
You and your partner were picked up together and are being questioned in separate rooms. Neither of you knows what the other is saying.
You are presenting
SLD.FUN/LESSON
0 of 8 have answered
The prisoner's dilemma
Your choice
You and your partner were picked up together and are being questioned in separate rooms. Neither of you knows what the other is saying.
Your choices and their payoffs
Rules · before you choose
Read across a row and down a column to see both payoffs. Values in points.
| Column · Column player | ||
|---|---|---|
| RowRow player | Stay silent | Talk |
| Stay silent |
|
|
| Talk |
|
|
Prisoner's dilemma — two suspects, separate roomsA recorded run of the real lesson, with fictional students. Read the lesson guide
Real lessons your class plays from their phones, while the big screen shows what the room decided.
Try the prisoner's dilemma
A practice run with fictional students. No real classroom or join code is created.
Try an answer on the phone. Lead the lesson from the screen.
On their phone
You are presenting
Setting up the room…
The classroom library
A curated library of classroom activities — game theory, economics, finance and physics — that a room plays rather than watches. Students join from their phones with nothing to install; choices stay private until they resolve on the projector; and the debrief happens over the room's own results. Every activity ships with Decka: sign up free, add one to your library, and run it in your next lesson.
Game Theory
14 activities
Payoffs, defection and cooperation, played by the room itself.
Prisoner's dilemma — two suspects, separate rooms · Chicken — four seconds on a single-track lane · The stag hunt — one day, two ways to spend it
Economics
17 activities
Markets, budgets and collective choices with real trade-offs.
Closing time at the market · The stag hunt — one day, two ways to spend it · Ten rounds in the pot
Finance
5 activities
Prices, bids and funds — where the money actually goes.
One lot, and the best loser sets the price · Spend the neighbourhood fund · What is a flat worth to you?
Physics
3 activities
Measurement, estimation and argument, run on the room's own readings.
One pendulum, everybody's stopwatch · How many table-tennis balls would fill this room? · A lorry and a car meet head-on
Ready-made lesson decks
Teach it tomorrow, from a deck that already plays.
Ready-to-teach decks for 26 lessons, each with a hook, how it works, the live activity and takeaways for the debrief. Plus decks for everyday teaching routines.
Each deck opens in your dashboard, ready to run. Change every word of it.
All Game Theory activitiesHow it works
- 01
Add it to your library
Sign up free and pull the activity from Decka's built-in classroom catalog — one click copies it into your own library, ready to run from Decka or inside PowerPoint.
- 02
Students join by QR
Everyone scans from the projector and plays in their phone's browser. No app, no account, nothing to install.
- 03
You run the room
You move the activity phase by phase: collection closes, the boards resolve on the big screen, and the debrief happens while the results are still up.
Ready to make your
presentations interactive?
Start free. No credit card required.