Which of the options A-E completes the image below?

enter image description here

enter image description here

  • $\begingroup$ Is that a puzzle you created yourself or is from some source? $\endgroup$
    – quarague
    Nov 20 at 10:51
  • $\begingroup$ @quarague Yes, myself. $\endgroup$ Nov 20 at 10:53
  • 1
    $\begingroup$ No source needed then :-) Maybe add a sentence in the bottom in case someone else wonders about the same thing. $\endgroup$
    – quarague
    Nov 20 at 10:55

1 Answer 1


I think



if we treat the non-grid lines as reflecting surfaces, the trajectories of beams trace out capital letters.

Thus in the first grid

a beam entering at the bottom left square, slightly above the middle of the left hand side and heading right (or bottom left, slightly left of the middle of the bottom side heading up) traces out a “B”

and in the second

a beam entering at the bottom left in the middle of the left side and heading right (or entering in the middle of the bottom square and heading up) traces out an “O”

and in the third

entering top left, middle of top side, heading down (or top right, middle of top side heading down) “U”

the fourth

entering bottom left, middle bottom side heading up (or top right, middle top side heading down) “N”

the fifth

entering top right, middle of right side heading left (or bottom right, middle of right side heading left) “C”


BOUNC suggesting an “E” or “Y” to follow. The B) grid with a beam entering in the bottom right middle of the right side and heading slightly above due left (or the middle right, middle of the top side, slightly above due left) gives an “E”

Or, visually:

Drawing of paths reflecting from mirrors in puzzle

  • $\begingroup$ What you say makes sense to me but what about the title, “THE INVISIBLE O”? What is special about O? $\endgroup$ Nov 19 at 17:04
  • $\begingroup$ That's the correct answer. Well done! $\endgroup$ Nov 19 at 17:08
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    $\begingroup$ @WillOctagonGibson The "o" was actually referring to an invisible ball that.. [the answer] $\endgroup$ Nov 19 at 17:09
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    $\begingroup$ I've added some pictures for you. $\endgroup$ Nov 20 at 11:19

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