Play / 9 games
Every game hidesa real idea.
You’re in Focus mode, so Play is hidden from the menus. The games still work here.
Chance
01 · Two variables
Guess the correlation
Ten scatter plots. Call r by eye. Within 0.10 keeps your streak alive.
02 · Probability rules
Three doors
The game show puzzle that fooled mathematicians. Play it, then run it 1,000 times.
03 · Counting and the binomial
Can you fake a coin?
Type 50 flips that look random. The streaks will give you away.
04 · Counting and the binomial
Serve math
Real 2025 ATP hold rates. See how a small edge on serve points wins sets.
Money
For learning, not advice.
05 · Random variables and expected value
The house edge
Spin a roulette wheel a thousand times, then watch a thousand players do it. The house never loses.
06 · Probability rules
Read the odds
Turn betting lines and prediction market prices into probabilities, and find the bookmaker's cut.
07 · Confidence intervals
Don't peek
Run an A/B test where nothing changed. Check it every day and watch fake winners appear.
08 · How spread out is it
The long run
98 years of real S&P 500 returns. Simulate 2,000 thirty-year futures and see why the average lies.
09 · The normal curve and z
Price an option
Simulate thousands of stock paths and watch the Monte Carlo price close in on Black-Scholes.
Ready for the real thing? Take a 10-question drill.