Concurrency Challenge

This challenge is built around a BPMN (Business Process Model and Notation) parallel gateway — the diamond-shaped symbol process diagrams use to mean "split into independent branches that must all complete." The page renders that diagram literally: a start event flows into a parallel gateway, which splits into two lanes, each ending in a task you trigger by holding a button down. The gateway only lets the token through — reaching the end event and completing the task — once both branches have been active, continuously, for three full seconds.

What this tests

Most automation practice sites test sequential accuracy: read a field, type a value, click next. This one tests genuine concurrency — driving two independent input threads at exactly the same time, the way a single human with a single mouse cannot. It is deliberately impossible to pass with one pointer: the two hold buttons sit far enough apart that a single cursor cannot be on both of them at once, and the validation logic watches raw pointerdown / pointerup state rather than trusting a click event, so there's no keyboard or CSS trick that fakes a sustained hold either.

Try it with

Anything that can drive two independent input streams into the same page at once: Playwright with two browser contexts (or two synchronized page handles) each issuing its own pointer-down sequence, two coordinated RPA bot instances, or — if you want to prove it to yourself first — two people, each holding one button.

Tips

Watch the status label under each branch button (Idle / Held / Released) and the shared progress bar at the join gateway — releasing either button before the three seconds are up resets the shared progress back to zero immediately, and the status line above the progress bar explains exactly what just happened. Append ?seed=42 to the URL for a repeatable run while you build your automation.