Tag Archives: hard

Puzzle 126: Yin-Yang Fences

And quickly another post to hide that terrible Domino Construction. In contrast, this one has a nice solving path, but will you find it?


Rules Solve as a standard Slither Link. In addition, all cells outside the loop must be connected, and there must be no 2×2-square of cells that is entirely inside or outside the loop.

Or see the instruction booklet.

Puzzle 124: Skyscrapers Domino Construction

Is it just me, or are there more uncommon types on this round than previously? Anyway, below there’s a Skyscrapers Domino Construction. Again these were on the 24 hours this year. This one is probably not typical, but I think it came out quite well.


Rules Place the given set of dominoes in the marked domino tiles. Whenever two dominoes touch by an edge, the adjacent numbers must be the same. Clues outside the grid are skyscraper clues: They indicate the number of visible skyscrapers when looking along the corresponding row or column from that point, where each number represents a skyscraper of that height. Skyscrapers are blocked from view by those of greater or equal height.

Or see the instruction booklet.

Puzzle 122: Paint By Threes

Continuing with the GP practice puzzles, here’s a Paint By Threes. I believe I’ve seen these more than once at the 24 hours, see Puzzle 121 for a link to the 2016 puzzles. There were a few on croco, too: Dreier-Nonogramm 1, Dreier-Nonogramm 2Dreier-Nonogramm 3. I tried to make this one a bit harder.


Rules Replace each circle with a non-zero number, divisible by three if and only if the circle is black. Then solve as a standard nonogram. I.e., shade some cells, such that the clues give the sizes of all blocks of shaded cells within that row or column, in the correct order.

Or see the instruction booklet. (In the competition presentation, white/black circles are replaced by white/gray squares.)

Puzzles 107, 108: Hochhausblöcke

To make it a full two weeks of post-LM posts, here are two more Hochhausblöcke. One with the maximal number of givens, one with the minimal number. (There are some more of each, but these are the nicer ones. The minimal one requires a well-placed deep case distinction, or I do at least.)

hochhausblock-max hochhausblock-min

Rules Place numbers from 1 to 4 in each cell so that each row and column of each 4×4-block contains all numbers 1 to 4. Circled numbers are valid skyscraper clues for the adjacent grid (for both adjacent grids in the central corners). Uncircled numbers are not valid skyscraper clues for the adjacent grid (for neither adjacent grid in the central corners).

Puzzle 106: Pentowords

We’re reaching the end of the series of LM practice puzzles. Pentowords is an interesting new (to me) type that was also on the mixed round. The one on the contest was built around a letter packing argument (though I only half saw that while solving), this one is quite different.


Rules Split the grid into the twelve different pentominos, and write each of the given words into one of the pentominos, left to right then top to bottom. Same letters must not touch by edge. Some letters are already given.