16th 24-Hour Puzzle Championship

The 16th 24-Hour Puzzle Championship was held in Budapest this weekend. As always the championship featured 14 puzzle sets to be solved over 24 hours, with each round lasting 100 minutes, with only 10 or 20 minute breaks in between. Neil Zussman was this year's winner with a slim 10 point lead over Robert Vollmert in second place and a 23 point lead over Michael Mosshammer in third place. Full results can be found here.

All puzzles of this championship (except round 11) can be found here. If you need an example of any of the puzzles, you can find the instruction booklets here.

I provided a set again this year. It was the 8th set to be solved between 11pm and 12:40am. The set contained 24 puzzles. It featured 12 genres, with one puzzle being a standard and one puzzle being a variant. I was originally going to include only 6 genres and two standard puzzles and two variants. I found it hard to decide on the genres to provide enough variation. I tried to keep all variations different per genre, to add to the variation in the round. I think it ended up being a good mix.
Robert Vollmert was the top scorer of the round with 810 points.

Puzzles can be found below

1. Araf (40 points, solved by 12 puzzlers)

I still have to work out a bit what can be done with this genre. I always enjoy solving them, but I think there's more to learn about them. That's why I decided to include it. I'm happy with the opening of the puzzle. It requires a little bit of insight, but nothing too hard. Without it there is no progress to be made. I decided to just order the genres alphabetically, ignoring the name of the variant. I hope this was clear and didn't needlessly get people stuck on the first page.

Rules:
Divide the grid into different regions along the grid lines so that each region contains exactly two numbers. The size of the region must lay strictly between these two numbers. This means that the size of the region can't be equal to either of the two numbers.

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2. Different Neighbours Araf (100 points, solved by 5 puzzlers)

This is the hardest puzzle in the set. It's the third time I wrote this variant. I'd supplied one to an Indian Puzzle Championship before and one was posted at Grandmaster Puzzles. I feel this variant is inherently difficult, mostly because region sizes are variable. This makes it harder to keep track of whether same size regions touch each other. I like how the puzzle turned out as the variant drives almost the whole puzzle, once you get past the opening.

Rules:
Divide the grid into different regions along the grid lines so that each region contains exactly two numbers. The size of the region must lay strictly between these two numbers. This means that the size of the region can't be equal to either of the two numbers. Two regions of the same size may not share an edge.

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3. Cave (30 points, solved by 18 puzzlers)

I like writing these puzzles. I didn't want this puzzle to be too difficult, so I tried to find an easier opening than I normally use. This seemed like an appropriate way to achieve that. It's still not overly easy, but it's not too hard to work through.

Rules:
Shade some cells to form a single orthogonally connected shape. The shape may not surround any unshaded cells; in other words, all unshaded cells must connect to the edge of the grid through other unshaded cells. All numbers are part of the shape. The numbers indicate the number of cells of the shape that can be seen from that cell, including the cell itself. Numbers can't see past unshaded cells.

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4. Product Cave (40 points, solved by 10 puzzlers)

This was the first puzzle I wrote of this variant. I never particularly enjoyed solving them, but I still though it was an interesting variant. I also thought it would add a different element to the set with multiplication.

Rules:
Shade some cells to form a single orthogonally connected shape. The shape may not surround any unshaded cells; in other words, all unshaded cells must connect to the edge of the grid through other unshaded cells. All numbers are part of the shape. The numbers indicate the product of the number of cells of the shape visible horizontally and the number of cells of the shape visible vertically from that cell, including the cell itself. Numbers can't see past unshaded cells.

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5. Doppelblock (30 points, solved by 24 puzzlers)

Doppelblock is another genre I really enjoy writing. It's a sentiment that comes back a lot in this set. Every author will more often come back to genres they enjoy writing. It also makes it easier to work on making variants. This puzzle is not necessarily difficult, but still needs some small insights.

Rules:
Shade two cells in every row and column. Then place the digit 1~5 in every row and column in the remaining cells. Numbers on the outside tell you the sum of the digits in between the two shaded cells in that row or column.

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6. Doppelblock Skyscrapers (50 points, solved by 9 puzzlers)

This variant I had obviously first seen in Roland Voigt's Skyscraper Contests, but I didn't actively remember that. I had to actually check back whether it had been done. It was a pretty tricky puzzle to write and probably caused me more problems then for you to solve. The problem is that you can just run out of useful clues. For example, if you know there's only one cell between two black squares, giving a clue about that square doesn't help you fill in any numbers. The end result is pretty nice though in my opinion.

Rules:
Shade two cells in every row and column. Then place the digit 1~5 in every row and column in the remaining cells. The digits represent skyscrapers of that height. Numbers on the outside tell you the number of skyscrapers visible between the two shaded cells in that row or column when looking from that side, ignoring skyscrapers outside the shaded cells. Larger digits block the view of smaller digits.

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7. Honey Islands (10 points, solved by 28 puzzlers)

This was one of the late inclusions in the set. I wanted to get the harder genres out of the way first. I then sent the set out for testing. Depending on the solving times, I would decide what other genres to include. As there really was only room for some simpler puzzles, I decide to include Honey Islands. The reason for that was that I had an idea for a variant. I tried to make the puzzle a bit aesthetically pleasing, by making the black squares look like 24 (sort of).

Rules:
Colour some cells so that the remaining cells form six separate areas of six connected cells.

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8. Hex Islands (20 points, solved by 20 puzzlers)

The variant is pretty simple. It leads to a bit more logic than normal. I wasn't sure if I could make one where there was no need for any black squares. My first successful try turned out to be a symmetric solution, which I didn't like. So I gave it another try, changed some hexagons around and this turned out. I's about half logic and half normal Honey Islands.

Rules:
Colour some cells so that the remaining cells form six separate areas of six connected cells. Each area must contain one hexagon.

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9. Maxi Loop (35 points, solved by 11 puzzlers)

This genre seems to be appearing in more places these days. It's a simple idea, so I'm not that surprised. It was originally invented by Naoki Inaba, but I've probably had something to do with it getting some more widespread attention since introducing it to my blog. This puzzle is a remake of a puzzle I had done before. I thought it worked well before and I don't think it's the same.

Rules:
Draw a single closed loop that travels through all cells horizontally and vertically. The loop doesn't touch or cross itself. Numbers in regions indicate the maximum number of cells the loop travels through in that region. This maximum must be achieved at least once.

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10. Maxi Loop 24 (45 points, solved by 8 puzzlers)

I'd used this variant before at the 24-hour puzzle championship. That time I went for a more aesthetic look. This time I wanted to create a puzzle without any clues. I wasn't sure how well it would work. I made a relatively easy opening and a key deduction to realise it wasn't necessarily illegal for size 2 and 4 sections to appear.

Rules:
Draw a single closed loop that travels through all cells horizontally and vertically. The loop doesn't touch or cross itself. Numbers in regions indicate the maximum number of cells the loop travels through in that region. This maximum must be achieved at least once. In this puzzle all 2 and 4 clues have been given.

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11. Pentopia (40 points, solved by 20 puzzlers)

I still like writing Pentopia puzzles. It's not that the logic changes much, but it's a fun logic to work with. You still run into interesting situations where a single clue can create interesting deductions and force pentominos in a nice way. I've stepped off clue symmetry a bit more recently just because I would see interesting things I could do, but not when preserving clue symmetry. Fun deductions always win over aesthetics with me.

Rules:
Place a number of different pentominos in the grid so they don't touch each other, not even diagonally. Reflections and rotations are seen as the same pentomino. Arrows in the grid indicate all orthogonal directions of the closest pentomino when looking from that cell. Cells with arrows can't be occupied by pentominos.

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12. Missing Pentopia (80 points, solved by 5 puzzlers)

I'd played around with this variant for a while, but didn't get anything very satisfying out of it. I thought the added element was interesting though. It's a tricky variant as it's easy to mistake a clue for a standard Pentopia clue. That's what makes it one of the harder puzzle in the set. It took a while to get a fun puzzle out of it.

Rules:
Place a number of different pentominos in the grid so they don't touch each other, not even diagonally. Reflections and rotations are seen as the same pentomino. Arrows in the grid indicate all orthogonal directions of the closest pentomino when looking from that cell. In each clue cell one arrow is missing. Cells with arrows can't be occupied by pentominos.

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13. Scrabble (50 points, solved by 22 puzzlers)

Writing word puzzles will never become my forte, but I wanted to give it a try. I tend to stick with themed word lists and try to design the puzzle around it. I wasn't sure which Scrabble style to go for as there seem to be three styles that are generally used. Either the cell with the first letter of each word is marked, a single letter of each word is given or all instances of a single letter are given. After a few tries, the last option turned out what was in my opinion the nicest puzzle.

Rules:
Place the given words in the grid so they can be read left to right or top to bottom. All words must be interconnected. Words other than the given words can't appear in the grid. All instance of the letter S have been given.

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14. Scrabble Blokus (75 points, solved by 9 puzzlers)

This Scrabble variant was a bit more interesting to me. I found a way to use some logic to get started and then it was mostly key to choose the right words to create the puzzle. I was pretty happy with how it turned out, although it tested a bit harder than I thought it would.

Rules:
Place the given words in the grid so they can be read left to right or top to bottom. All words must be interconnected. Words other than the given words can't appear in the grid. All places where two words touch solely by a corner have been marked by a dot.

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15. Simple Loop (10 points, solved by 35 puzzlers)

This was another one of the last inclusions in the set. There isn't much to say about this puzzle than it's a Simple Loop.

Rules:
Draw a single closed loop that travels horizontally and vertically through all white cells. The loop is not allowed to touch or cross itself.

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16. Toroidal Simple Loop (30 points, solved by 18 puzzlers)

This seemed like the most obvious variant to this genre. I'm not sure whether I've actually seen it before. It just adds a little bit of a tricky twist to the genre, but the logic really doesn't change.

Rules:
Draw a single closed loop that travels horizontally and vertically through all white cells. The loop is not allowed to touch or cross itself. The grid is toroidal; this means that the loop can pass through the edge of the grid and continue on the other side.

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17. Snake (35 points, solved by 9 puzzlers)

This Snake puzzle is like many of my Snake puzzles. So for those who've solved mine before, you'll recognise the style. There's certain things I like to do with them. This one was fun to write and pretty easy to execute. There's a bit of global thinking involved, having to understand where the Snake is going before you can draw some parts in.

Rules:
Place a one cell wide snake in the grid so it doesn't touch itself, not even diagonally. The head and tail of the snake are marked with a circle. Numbers on the outside indicate the number of cells in that row or column that are occupied by the snake.

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18. Easy as ABC Snake (45 points, solved by 6 puzzlers)

I'm always surprised by the lack of clues needed to write these puzzles. Because the Snake fills itself in, you don't actually need clues to know where most the letters go. The key is always to set up a good opening and then just use the letters to guide it along and possibly fix some uniqueness issues.

Rules:
Place a one cell wide snake in the grid so it doesn't touch itself, not even diagonally. The snake is built of repeating letters ABC in order (...-A-B-C-A-B-C-A...). The head and tail of the snake are marked with a grey square. The head and tail can contain any letter. Letters on the outside indicate the first letter seen in that row or column from that side.

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19. Star Battle (30 points, solved by 21 puzzlers)

I always enjoy writing Star Battle puzzles. The rules are simple, but it still can lead to some intricate logic. I obviously started by placing the 2 and 4 shaped regions and then wrote the puzzle around that. I thinked it turned out nicely. There's no real difficult steps in this puzzle, but you do need to see to opening to start as there's little progress to be made without it.

Rules:
Place two stars in every row, column and marked region. Stars can't touch each other, not even diagonally.

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20. Sea Battle (45 points, solved by 14 puzzlers)

I wanted to revisit this genre as I hadn't really looked at it since I wrote it for my LMI Hybrids test. They generally turn out pretty difficult, so I wondered how I could fix this. That's why I decided to go with a single ship fleet, solely made up of two cell ships. It took me a little while to figure out the size of the grid had to always be divisible by three, after I had already tried writing a 10 by 10 puzzle. I thought 9 by 9 would be a bit small, so I went for a 12 by 12 grid. I don't think the puzzle is necessarily hard, but it's different logic, so it is easy to overlook some of the logic involved.

Rules:
Place the given fleet in the grid so that each row, column and marked region contains exactly tow ship. Ships can't touch each other, not even diagonally. Ships may not lay across borders of regions.

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21. Sudoku (30 points, solved by 18 puzzlers)

I don't think I'll ever really get the hang of writing classic Sudokus. Variants are more my style, even if it's just a Jigsaw Sudoku. I have trouble getting the logic working for me in a satisfying way. This Sudoku is probably nothing special, but should still be fun to solve.

Rules:
Place the digits 1~9 once in every row, column and marked 3x3 region.

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22. Consecutive Clone Sudoku (60 points, solved by 11 puzzlers)

This is one of my own variants that I enjoy writing. I chose this variant as they don't normally turn out too hard. Some Sudoku variants I can really turn up the difficulty, but I think I'm a bit more limited in this variant. It's mostly because it's harder to see whether you're creating an invalid puzzle that no longer has a solution.

Rules:
Place the digits 1~9 once in every row, column and marked 3x3 region. Cells in the same position in both grey figures must be consecutive.

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23. Tapa (25 points, solved by 21 puzzlers)

I wrote a Tapa with a comparable layout before. But I liked this layout with a lot of open space. The four 1/3 clues on the outside weren't originally planned. When I had three in the first design, I edited the puzzle a bit to add a fourth 1/3.

Rules:
Shade some cells to form a single orthogonally connected shape. The shape can't occupy any 2x2 area anywhere. Numbers in the grid tell you the number of consecutive cells that must be shaded around it. If there's more than one number in a cell, these consecutive blocks must be separated by at least one empty cell. Clue cells can't be shaded.

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24. Circled Tapa (50 points, solved by 2 puzzlers)

This was actually the first puzzle I wrote for the set. I enjoyed writing the first puzzle of this genre and wanted to test out if I could write a puzzle where you didn't easily know which colour each cell would be. It took a while to find a satisfying opening, but I think this one works well. This of course makes the puzzle a bit harder to solve as you can do very little with the other clues if you can't tell which colour the cells are.

Rules:
Fill some cells with black and white circles to form a single orthogonally connected shape. The shape can't occupy any 2x2 area anywhere. Same colour circles can't touch each other by a side. There are black and white clue cells. White clue cells indicate the number of white circles in consecutively filled cells around it. Black clue cells indicate the number of black circles in consecutively filled cells around it. If there's more than one number in a cell, these consecutive blocks must be separated by at least one empty cell. Each number indicates a section of at least length one.

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