STEM
RaceForge
Two tasks. One shared counter. What could go wrong? Predict the smallest value a data race can produce, watch the exact interleaving that loses an update, then wrap it in an actor and see the race vanish. RaceForge enumerates every possible interleaving on your device — no guessing, no magic — so you can feel exactly what Swift 6 is protecting you from when it checks concurrency at compile time. Ages 15–18.
▶ Play it nowBuilt for sittings of about 25 minutes on the screen. That is our design budget, not a measurement.
#4a6cd4 Characters who teach
Meet the cast
RaceForge breaks a programming bug called a data race into its parts. Sheara is a value two tasks both change, Trice is a step that looks like one action but is really three (read, add, write), and Baton is the order the tasks happen to take turns in. Isla, the mentor, is the fix: a boundary that lets only one task touch the value at a time.
Sheara
Shared state — one variable both tasks can read and write; the moment it is shared AND mutable, a race is possible
Trice
The non-atomic step — ‘counter += 1’ is read-modify-write, three operations another task can land in the middle of
Baton
The interleaving — the exact order the two tasks' steps happen to run in; some orders are fine, some lose updates
Isla
The actor — an isolation boundary that serialises access so only one task touches the state at a time; each operation becomes atomic and the race cannot be expressed (the idea behind Swift 6 strict concurrency)
What's inside
Learning goal
Two tasks. One shared counter. What could go wrong? Predict the smallest value a data race can produce, watch the exact interleaving that loses an update, then wrap it in an actor and see the race vanish. RaceForge enumerates every possible interleaving on your device — no guessing, no magic — so you can feel exactly what Swift 6 is protecting you from when it checks concurrency at compile time. Ages 15–18.
Mentored by Isla — no data leaves the device.
How RaceForge handles your kid's data
- ✅ All progress, settings, and AI-generated content stays on the device
- ✅ No analytics, no tracking, no third-party SDKs
- ✅ Free — no ads, no in-app purchases
- ✅ No personal information collected from children — in line with COPPA (updated by the 2026 FTC amendments)
- ✅ No chat with strangers — play-together rooms use a short code and preset emotes, never typed messages