Rays▶Play

Three atoms hide inside a sealed 6×6 box. Fire rays in from the edges and read what happens — some are swallowed, some bounce straight back, some come out somewhere else entirely. Work out where the atoms are, using as few rays as you can.

How to play

Tap any square on the border to fire a ray inward. An H means the ray hit an atom head-on and was absorbed. An R means it came straight back out where it went in. Otherwise it leaves somewhere else, and both the entry and the exit are tagged with the same number so you can pair them up.

A ray is absorbed when an atom sits directly in its path, and it turns 90 degrees away from any atom sitting diagonally in front of it. Tap three inside squares to mark your guess, then press Check. Solving scores 15 minus the number of rays you fired, never less than 3 — so deduce, don't spray.

Tips & strategy

Start with rays that pass clean through. A ray entering one side and leaving directly opposite tells you an entire lane is empty, and two or three of those carve the board down faster than any single clever shot. Negative information is cheap here and it is what makes the later shots decisive.

An R is louder than it looks. A ray coming straight back usually means an atom sits diagonally beside the entry square, because that geometry turns the ray around before it ever gets in. So an R on the border narrows the candidates to a couple of squares near that edge, which is often more than an H tells you — an H only says the atom is somewhere along that lane.

When two rays exit at the same numbered pair, trace the corner they must have turned. A single deflection needs exactly one atom diagonally adjacent to the turn, and you can often place that atom precisely by intersecting the paths of two different deflected rays. Two deflections in one ray means two atoms, which is rarer and usually pins them both.

Because your score is 15 minus the rays you fire, the difference between a good player and a great one is knowing when to stop. Once the surviving candidate positions are down to one arrangement, fire nothing more — an extra confirming ray costs you a point and tells you what you already knew.