# Puzzle 37: Höhlenbahnhöfe

Last of the set. This is a type that really benefitted from preparation, it takes some getting used to. The contest puzzle ended up going mostly smoothly, unfortunately I ended up spending a lot of time resolving a non-contradiction in one part of the puzzle.

Rules Shade some cells to leave an orthogonally connected set of cells (the “cave”) that doesn’t enclose any shaded cells. All clues must be within the cave. Then draw a path through the cave that travels horizontally or vertically between cell centres that visits all unclued cave cells and doesn’t touch or intersect itself. This path passes through some (at least one) consecutive clues in ascending order, starting at 1 and going straight through any clue. The clue 1 is in the second cell of the path, the highest clue as in the second-to-last cell of the path. The remaining clues are usual cave clues: they count the total number of cave cells that can be seen in horizontal or vertical direction from that cell, including the cell itself.

See the puzzle wiki for German rules (that allow the usual Bahnhof crossings) with an example.

# Puzzle 36: Masyu Reconstruction

Second to last in the series, this is a Masyu Reconstruction. The one on the contest turned out to be pretty similar in style. The type could also go another way, with a heavier focus on making a puzzle unique with few givens.

Rules Place black and white pearls in some cells to form a valid Masyu puzzle, such that the clues in a row or column are equal to the outside givens in that order.

# Puzzle 35: Hitori Rundweg

Here’s another one from the LM preparation. EDIT: new version fixing an ambiguity.

Rules Shade some cells, such that there’s at most one unshaded copy of any number within a row or column. Shaded cells must not share an edge. Then draw a single loop that travels horizontally and vertically between cell centres that visits all unshaded cells.

# Puzzle 34: 123-Box

Another training puzzle, this is a 123 box, a variation on the ABC box that was introduced at the German Logic Masters.

Also, I’ve posted a Doppelter Rundweg on the puzzle portal. That one is probably the hardest puzzle I’ve constructed to date.

Rules Put a number from 1 to 3 in each cell. The hints correspond exactly to connected groups of equal numbers within that row/column. A number clue stands for a group that consists of that number, or is that size, or both. A question mark clue stands for an arbitrary non-empty group.

There’s an example with the (German) instructions on the puzzle wiki.

# Puzzle 33: Sackbahnhöfe

Saturday was the German Logic Masters in Stuttgart. I’m mostly happy with how it went, placing fifth after last year’s seventh in what was probably a stronger field. Though missing place four and thus the A-team for London by a single point is a bit hard.

The puzzles were great, I particularly enjoyed the “special” rounds, such as the Doppelter Rundweg or the final Vier Jahreszeiten. They’re available now as online contests.

I had a bit of time this year and made some puzzles in preparation that I’m going to post over the next couple of days. The first is a Sackbahnhöfe.

Rules (from the booklet) Draw a loop with some branches into the grid, which visits every field of the grid. The loop crosses itself only at the marked crossings. Fields with numbers are railway stations. The loop branches in the field before the railway station. There may be only one branch in a field. The branch then moves straight through the railway station, and ends in the field after it. The branches with the stations have to be in increasing order along the loop.

See the contest page for instructions that include an example.

# Puzzle 32: Hitori

Here’s a Hitori puzzle that I made a while back. Which gives me an excuse to advertise the German Logic Masters that take place in Stuttgart on Saturday, which include a Hitori-themed round among others. The instructions were published this weekend, it promises to be an excellent set of puzzles. What’s more, this year the contest will also be offered online with a slight delay, see this forum thread.

# Puzzle 31: Pyramid, knapp daneben

Here’s a “knapp daneben” pyramid puzzle, i.e., all clues are off by one. Please excuse the slight asymmetry, it’s because the bottom clues including gaps were meant to be transferred from other puzzles. It’s fall-out of a puzzle contest I’ve helped write, together with the Berlin Stammtisch, which will be held on the weekend of June 28. See the instruction booklet.

Rules Place a number from 1 to 9 in each cell, such that for any two horizontal neighbours, the number between and above the two is their sum or their difference. In gray rows, all numbers must be distinct, while in white rows, there must be at least one pair of duplicate numbers. All given numbers are off by one.