Plumber

Pipe pieces sit scattered across the grid at random angles. The job is turning each until their ends meet in a single unbroken route from the inlet to the outlet. Straightforward in principle, except every layout contains a piece that appears to connect and quietly leads to a dead end.

The quickest method is working inwards from both ends, because the segments touching the inlet and outlet have the fewest possible orientations. With both sides locked down, the middle usually has only a handful of arrangements left, which the eye can sort through in seconds.

Some stages run a clock, others count rotations, so spinning pieces at random carries a real cost. The habit worth building is studying the whole grid before touching anything — the opposite of what most people do while the early, easy layouts still forgive it.