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enter image description here

The original Masyu rules apply.

  1. Make a single loop with lines passing through the centers of cells, horizontally or vertically. The loop never crosses itself, branches off, or goes through the same cell twice.
  2. Lines must pass through all cells with black and white circles.
  3. Lines passing through white circles must pass straight through its cell, and make a right-angled turn in at least one of the cells next to the white circle.
  4. Lines passing through black circles must make a right-angled turn in its cell, then it must go straight through the next cell (till the middle of the second cell) on both sides.

Thanks to @Deusovi for playtesting this puzzle! :D

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Just noticed that this puzzle - although previously solved - has no step-by-step solution in place. So to assist other puzzlers in understanding the process involved in solving it, here's a write-up of the logic...

Step 1:

Firstly, mark up the trivial initial lines: the two corner black dots where the lines must extend through the nearby white circles and then bend upwards, and the three black dots in column 11, which must have lines going off to the left, forcing the whites to their south-west to be crossed horizontally, in turn forcing the lines upwards from each of the black dots.
Solution step 1

Step 2:

To proceed further with any confidence, we need to force a contradiction. Let's consider what would happen if the white circle in r10c9 is crossed vertically. Doing so would force the line upwards to join with the white circle in r8c10, forcing the path in the bottom-right corner into the configuration shown in the diagram below via several steps of forced logic. However, the place to focus on here is actually the two black dots in r9c8 and r11c7, whose horizontal lines are forced to go left. The lower of the two then forces the white circle in r12c6 to be crossed horizontally, leaving no valid way for the black dot's vertical line to be satisfied:
Contradiction in solution step 2.

Therefore, the white circle in r10c9 must instead be crossed horizontally. Doing so forces the line's path in much of the right-hand side of the grid through subsequent chained reasoning:
Solution step 2

Step 3:

Next consider the white circle in r6c5. If this were crossed vertically, there is no way to continue the line legally (either turning to join the black dot with a 1-length line or continuing upwards and completing a loop). Thus, this white circle must be crossed horizontally. This leads to some further forced logical deductions in the top-left corner:
Solution step 3a

...which cause further knock-on deductions that end up completely resolving all line segments north-east of the grid's main diagonal (through avoiding forming closed loops):
Solution step 3b

Step 4:

The black dot in r11c7 can also be fully resolved now. This brings us to a position very similar to that in Step 3, above, in that the white circle in r10c5 must be crossed horizontally as there is no legal way to do so vertically. Doing so ends up resolving all but the bottom-left corner:
Solution step 4

Step 5:

Now we note that the line from the white circle in r12c6 must bend downwards, as bending upwards would cause a large closed loop to be formed, taking up the entire right-hand-side of the board:
Solution step 5a

...and then finally we note that the horizontal line from the black dot in r11c3 cannot go left, or this forces the white circle to its southwest to be crossed horizontally and the two ends of the line can never be joined:
Contradiction in solution step 5

Instead the black dot's line must go right and the rest of the line segments are placed by forced logic to produce the single completed loop!
Final solved grid

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    $\begingroup$ Ooh! Thanks for bumping this old puzzle haha, and with these great explanations, I should reward you with the tick! :D (hope @Jafe doesn't mind tho.. ><) $\endgroup$ – athin Apr 1 at 3:23
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Haven't done these before, but I think I have a solution:

enter image description here

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  • $\begingroup$ Seems to follow all the rules. $\endgroup$ – PieBie Jul 5 '19 at 9:53
  • $\begingroup$ Yep this is correct :) $\endgroup$ – athin Jul 5 '19 at 11:07

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