Blind Corners (Arkai)

Blind Corners is one of the daily deduction puzzles on Arkai, a small portal of free browser games with no account, ads or third-party code.

Each day brings three boxes, Easy, Medium and Hard, worked out from the date so everyone plays the same ones. Each box is a square grid with a few hidden mirrors set at angles. Arrows around the edge fire a beam in; it turns at every mirror it hits, and all you learn is the port where it leaves, shown as a matching number and colour at both ends.

You mark mirrors on the grid as slashes or backslashes, and the game runs the selected beam through your marks so you can see whether it explains what happened. Ports whose beams your marks do not yet explain are outlined in red. Every beam costs one point and a wrong check costs two, and finishing within par, which is what Arkai's own solver needed, earns a star. Any layout that no beam could tell apart from the real one counts as solved. Results can be shared without spoilers, and earlier days stay playable.

The puzzle is a cousin of the classic Black Box board game. It suits players who enjoy careful experiments and reasoning about paths you cannot see.