TWENTY-NINE DAYS
You wake to a voicemail: the world ends on the 29th, and only you were told. You live alone. You work in the city. The hours the investigation needs are the hours your life already spends, and rent does not care what you found out.
A narrative incremental played in days: allocate your waking hours, keep the job or don't, and decide who to tell.
Early build — chapters one and two, about half an hour. Progress saves in your browser. More chapters are being written; your save carries forward.