Blackbox play online

A number of balls are hidden in a rectangular arena. You have to deduce the positions of the balls by firing lasers positioned at the edges of the arena and observing how their beams are deflected.

Beams will travel straight from their origin until they hit the opposite side of the arena (at which point they emerge), unless affected by balls in one of the following ways:

A beam that hits a ball head-on is absorbed and will never re-emerge. This includes beams that meet a ball on the first rank of the arena.
A beam with a ball in its front-left square and no ball ahead of it gets deflected 90 degrees to the right.
A beam with a ball in its front-right square and no ball ahead of it gets similarly deflected to the left.
A beam that would re-emerge from its entry location is considered to be reflected.
A beam which would get deflected before entering the arena by a ball to the front-left or front-right of its entry point is also considered to be reflected.

Beams that are reflected appear as a R; beams that hit balls head-on appear as H. Otherwise, a number appears at the firing point and the location where the beam emerges (this number is unique to that shot).

You can place guesses as to the location of the balls, based on the entry and exit patterns of the beams, once you have placed enough balls a button appears enabling you to have your guesses checked.