The frame keeps everyone alive. Learn why.
Twelve levers. Each one is a signal, a set of points, or a facing point lock. Pull one by tapping it — it moves to Reverse; tap again to put it back to Normal.
You cannot pull a lever out of order. The frame is wired so that an illegal pull simply won't go — and it will tell you exactly which lever is stopping it. That message is the whole game: read it, fix the order, try again.
A cleared signal locks its points in place. A train on the track locks the points too — you cannot move anything a train is standing on. Two signals that would send trains at each other can never both be off at once.
Set the road, lock it, then clear the signal for the train that's coming. Watch the little clock — a train that reaches a red signal is checked: it stops and waits, and your box loses its perfect record for the day.