An entry into Fortnightly Topic Challenge #41: Short and Sweet

The classic evil supervillain has built a superlaser. He has you tied up while he is monologuing about his evil plans.

However, you have managed to sneak your phone in with you. You've managed to purchase 16 mirrors that are strong enough to reflect the beam! You can text your sidekick how to orient the mirrors throughout the villain's lair to destroy the laser's power source.

However, the mirrors can't be moved once they're placed due to the precise angle required, and your sidekick has already placed two.

You have a map of the villain's lair, as well as where the sidekick has already placed some mirrors.

enter image description here

The laser fires where the arrow pointing in is. Your job is to reflect it where the arrow pointing out is so you can destroy the laser's power source. A square represents a room, and a diagonal line represents a mirror.

There are some restrictions on how to place the mirrors, though.

  1. Mirrors take up the whole room, and must be placed diagonally, from a corner to the opposite corner.

  2. You must place a mirror in every room, or the laser will be too strong and burn through a mirror.

  3. Mirrors reflect the laser at a precise 90 degree angle.

  4. The laser must be in every room, or it won't be strong enough to destroy the power source.

How do you have your sidekick place the mirrors, so that when the supervillain's laser fires, it is reflected and destroys his power source?

No hints, it's not too hard as it's meant to be solved within 5 minutes, although it probably will be solved quicker.

  • $\begingroup$ I wonder what the supervillain's evil plan was, firing a superlaser into his own lair like that... OP, I don't suppose the villian managed to finish his monologue before gabbo1092 solved the puzzle? $\endgroup$ Nov 14, 2018 at 22:03
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    $\begingroup$ @deepthought everyone knows supervillain monologues last until the hero figures out something to do about their evil plan! $\endgroup$ Nov 15, 2018 at 0:13

2 Answers 2


I believe this way would work:

enter image description here

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    $\begingroup$ As predicted, solved in 5 minutes. Well done! $\endgroup$ Nov 14, 2018 at 20:08
  • $\begingroup$ It was perfect for the challenge! Well done $\endgroup$
    – gabbo1092
    Nov 14, 2018 at 20:08
  • $\begingroup$ I was about to comment that it is impossible to put the laser beam through the room at gbc yrsg, but I didn't consider that the mirrors are qbhoyr fvqrq. $\endgroup$ Nov 14, 2018 at 20:11
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    $\begingroup$ (rot13) svthevat bhg gur zveebef jrer qbhoyr fvqrq jnf cneg bs gur punyyratr $\endgroup$ Nov 14, 2018 at 20:16

Another solution is:

mirror solution

This is different starting at (2,2).

  • $\begingroup$ I believe these are the only two solutions - every piece after (2,2) is forced. $\endgroup$ Nov 15, 2018 at 1:06

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