This question is part of the best-puzzle award series.
What are your nominations for the best puzzles, here on Puzzling.SE, of the second quarter (Apr/ May / Jun) 2016?
Suggested guidelines for nomination:
Nominate each individual puzzle in a separate answer, so they can be upvoted/downvoted separately.
No more than 3 nominations per person.
Don't nominate your own puzzles.
Before you nominate a puzzle, check to see if someone else has already nominated it. If they have then add to that nomination as a comment (or edit it), instead of nominating the same puzzle again.
In your nomination, explain what it is that (in your opinion) makes the nominated puzzle such a good one.
Also remember: This, as all other posts of the best-puzzle awards series, is an open ended list. If you discover any high quality puzzle which you think deserves to be listed under the 'best-of-site', nominate it in the best-puzzle post of the according time period.
Some lists to help jog your memory (your nomination doesn't have to be from these lists):
- Algorithmically selected "best of":
- Best by votes/views: