Ghost in the Stack — real bugs, real debugging, one case at a time.
You are on call, and something in production is wrong. Each case is an incident worked the way a senior engineer would work it: the alert, the shape of the system, the logs, the metrics, what shipped, a hypothesis, a breakpoint, a walk through the code with a debugger, the root cause, a fix — and the tests. It is not a quiz with broken code on it. Every wrong call is answered with why, and you try again.
Play Ghost in the Stack →Free, and no account needed — play as a guest. Runs in the browser — nothing to install.
| Step | What you do |
|---|---|
| Alert | read the incident and make the first call |
| Evidence | open the flow, logs, metrics and deploys; pin the clues |
| Hypothesis | say what you think is wrong, and hear why |
| Breakpoint | pick the line to pause on |
| Debugger | step over, into and out, frame by frame |
| Root cause | tell the symptom from the cause |
| Fix | edit the code and run the tests |
There is no clock. Restarting the service, wrapping it in a try, reaching
for .get() — the fixes that make the symptom go away without touching the
cause fail their own tests, the way they would in a real review.
The board runs easiest first. Easy cases teach the moves; medium ones add the whole system to read and a second hypothesis; hard ones add red herrings that look alarming.
A rating out of a hundred, and speed is not part of it. It is the mean of five:
Anyone who has been handed a bug they did not write. The code in the cases is Python, but the method — evidence before theories, the cause before the fix — is the same in any language.
You are told why it is not the right call, and you try again. Only your first answer counts towards the rating, so the lesson is free and the score stays honest.
Yes. Every game on SULULU is free and there is nothing to buy.