Room Numbers
Eight rooms, four-digit keypads, and a backup generator that can only carry two circuits. The number you need for a code is painted in a room that has to be lit before you can read it, so the puzzle is never “find the code”. It is “decide what to leave in the dark”.
Power is the real key
Every locked door wants four digits, and every digit lives on a screen or a sign inside a room. The main feed is down, so those rooms only read out when the backup generator is feeding them, and the generator tops out at two circuits. Reading a code is therefore a routing problem: pull power off a corridor you have already crossed, push it into the room you still need, and walk back through the dark you just made.
The two-circuit limit is not posted anywhere at the start. The panel just says BACKUP GEN, and the first time a player throws a third breaker it buzzes, flashes OVERLOAD, and drops everything. Only then does the label change to read 2 CIRCUITS MAX. The failure teaches the rule, and the sign afterwards is only there so the lesson sticks.
One way forward
Doors drop behind the player and refuse their own code afterwards, so the facility never lets you undo a leg of the route. That constraint is what makes the power choices matter: if the answer were still reachable behind you, cutting a circuit would cost nothing.
Not every number is something you can see. One code arrives over an intercom as a run of beeps, with a long tone standing in for zero, so a room with no working screen still has an answer in it. The run ends on an elapsed-time readout and a NIGHT SHIFT OVER card, which turns a short course exercise into something players compare runs on.