On-Call: 3AM Incident Mystery

Now in English: the game follows your device language (English or Korean), and you can switch anytime from Language in the game info on the title screen.

The pager goes off at 3 AM. As the on-call engineer, spend one night's worth of coffee buying clues, deduce the cause of the outage yourself, and run the right response card before service health hits zero. A deduction roguelike; one run takes 5–15 minutes.

■ One night · Convenience store before your shift — spend 5 trust points on relics and check how many coffees you have tonight. · Alerts — 03:02, 04:17, 05:34. Three incidents a night; the third comes with an anomaly. · Investigate — spend coffee to open error logs, metrics, deploy and job history, and coworkers' chat testimony. Health keeps dropping in real time while you dig. · Deduce — each clue points to four causes, and two different clues overlap on exactly one. Tap to fold the suspect chips you've ruled out; the game won't eliminate them for you. · Respond — match the top line of a card ("which symptom this fix is for") with what you saw in the clues. Tap twice to run it: right and the service recovers, wrong and health takes a big hit. · Morning — the postmortem records average MTTR, accuracy and a grade, and you earn honor. If health hits zero, the night ends in a SEV-0 company-wide outage.

■ Coffee is the night's budget Coffee doesn't refill per incident; all three incidents share it. Besides opening clues (log 1, metrics 1, deploy history 1, chat 2), coffee pays for insurance (halves the next wrong-answer penalty), calling a coworker (rules out two innocent suspects) and a sip (+5 health). Out of coffee, you can pay health for clues.

■ 16 causes, 16 response cards Causes and cards match one-to-one. Each cause has one decisive source a practitioner would open first, and opening it prints a signature line. Every cause you solve is recorded in the incident handbook as "this symptom, this fix". As your shift count grows, the pool expands from 8 to 16 causes.

■ Anomalies · Source down — one of the four sources is unavailable. · Stale clue — one source shows a snapshot from hours ago; check the collection time and filter it yourself. · Compound incident — two causes are tangled, and you must fix both to recover.

■ 15 relics The store opens three times a night with three random relics on the shelf (reroll 2P). Relics and trust points last only that night, so every shift starts from scratch. Some relics come at a price, like Caffeine Overdose (+3 coffee for the night, but wrong answers cost 1.5×).

■ On-Call Pager widget Put the pager on your Home Screen (small or medium) or Lock Screen. During a night it shows the incident number, the in-game clock, service health and coffee left; in the morning, last night's grade, incidents resolved, average MTTR, accuracy and your total honor. While you play free, it also shows whether tonight's free shift is still open.

■ Saving Shift count, honor, the handbook and any run in progress are saved on the device. Close the app mid-incident and you pick up with the same health and clock.

■ Price and connection · Free to start. One night shift per day is free; the one-time Full Unlock purchase lets you take as many shifts a day as you want. No ads, no subscriptions. · If you bought the app before it became free, everything is unlocked automatically. · Works entirely on the device — no internet connection, account or login. No personal data is collected. · Real-time synthesized sound and iPhone haptics. Mute from the title screen.