A different Murdoku becomes the case of the day at midnight UTC and stays there for twenty-four hours. Everybody solving it that day is solving the same floor plan, the same cast and the same clues, which is the point: a time is only worth posting if somebody else can post theirs against it.
Nothing about it is gated. You do not need an account, the case is not harder because you arrived late, and there is no streak to protect — come back when you feel like a puzzle rather than because something is counting.
It would be easy to generate a new puzzle each day from the date, and it would be wrong. The generator searches for a case within a time budget, which means a faster machine gets through more attempts and settles on a different puzzle from the same starting point. Two people on the same day would find different cases, and every shared time, every conversation about the tricky bit in the middle, would be about nothing.
So the daily rotates through the hand-built casebook instead. It is a pure function of the date — your device and ours reach the same answer without ever talking to each other — and the cases are the written ones rather than machine output.
Every case gets its turn before any case gets a second one, so a full pass takes as many days as there are cases: months, not weeks. When the casebook is exhausted the order is reshuffled, so the next pass through it is a genuinely different sequence rather than the same run again.
If you have never played, the daily is a reasonable place to start but not the gentlest — it takes whatever case comes up, which might be a twelve-by-twelve. The rules take about a minute to learn and never change: each person stands in their own row and their own column, and the room holding the victim contains exactly one suspect. That suspect is your murderer.