# List of Snake variants

There are a lot of Snake variants. In fact, there had been three occasions of Serkan Yürekli's Snake Variations Contest before. WPC 2017/Round 11 was a round solely consisted of Snake variants. Refer to Snake for the standard definition of the word "snake" in this article. Rules are slightly modified to unify how the rule statements start.

### Dotted Snake

Invented by Zoltán Horváth (Hungary) in 2003, which is surprisingly earlier than Striped Snake. [1] First appeared on WPC 2005/Part 5.

Place a snake of a given length in the grid. The snake cannot go through black cells. Every third cell (3rd, 6th, 9th and so on) of the snake is dotted. The numbers outside the grid show the number of dotted cells in the corresponding row or column. The first and last cells of the snake are given.

(Example (length 18) from WPC 2005 IB)

### Striped Snake

First appeared on the IPST 2004, written by Andrey Bogdanov (Russia). [2]

Place a snake in the grid. The snake consists of neighbouring cells of two alternating colours. Numbers to the right show the number of grey cells in that row. Numbers below the grid show the number of black snake cells in that column.

(Rules from 2011 UK Nationals IB, example from janko.at)

### Snake BY

First appeared on Forsmarts Issue 29 (2006).[3] Invented by Vladimir Portugalov (Belarus).

Place a snake in the grid. Each outlined region must contain exactly 3 cells occupied by the snake. The regions that contain the head and the tail of the snake are marked by grey colour.

(Rules and example from Forsmarts booklet)

• Sometimes the name Regional Snake is given to a variation of Snake BY where (i) heads and tails are given and (ii) solvers must determine the number of cells in each region that are occupied by the snake (3 in the original). For example, a puzzle from WPC 2018/Round 11.

### Persistence of Memory

Invented by Serkan Yürekli. First appeared on Oğuz Atay Puzzle Contest 5 (2009).

Place a snake in the grid. The path must use at least one cell from each outlined and shaded region. If two or more regions have the same shape and orientation, then the path must go through these regions exactly in the same way, including the points where it enters and leaves these regions.

(Rules and example from WPC 2019 IB)

### First Seen Snake

First appeared on Puzzle Jackpot [4] in 2011. The author was Serkan Yürekli (Turkey).

Serkan's inspiration for the inclusion of First Seen rule comes from Andrey Bogdanov's First Seen Coral. [5]

Place a Snake in the grid. The numbers outside the grid indicate the lengths of the first snake segment in that row or column.

(Rules and example from WPC 2018 IB)

### True-False Snake

First appeared on 2013 UK Nationals. [6] Author of the puzzle was Prasanna Seshadri (India).

Place a Snake in the grid. Additionally, the numbered arrows in the grid indicate the number of cells the snake visits in the direction of the arrow. If the snake does not pass through a clue cell, then that clue is true, otherwise, it must be false, i.e. cannot be true.

(Rules and example from WPC 2017 IB)

### Regional Snake

First appeared on WPC 2013/Part 7. Author of the puzzle is currently unknown.

Place a snake in the grid. Numbers in each of the regions surrounded by thick lines denote the number of cells occupied by the snake in that region.

(Rules and example from WPC 2013 IB)

### Snake in the Naval Forest

Hybrid with Tents and Battleships. First appeared on forsmarts 12th Anniversary Contest (2014). Author of the puzzle was Vladimir Portugalov (Belarus).

Attach a tent to each tree, in a horizontally or vertically adjacent cell. Cells with tents do not touch each other, not even diagonally. Additionally, place the given set of ships into the empty cells of the grid. Ships cannot touch each other, not even diagonally. Futhermore, raw the snake through all the cells that are left empty. Its head and tail are shown by the circles. Snake is 1-cell wide an doesn’t touch itself even at a point.

Clues outside the grid show the number of occupied cells either by ships or by the snake in the corresponding row or column.

(Rules and example (Battleships) from WPC 2015 IB)

### All or None Snake

First appeared on WPC 2018/Round 5. Author of the puzzle was Deb Mohanty (India).

Place a snake in the grid. Additionally, if one instance of a letter is part of the snake, all instances of the letter are part of the snake. Length of the snake is given.

(Rules and example (Length=23) from WPC 2017 IB)

### BOA Snake

First appeared on WPC 2018/Round 5. Author of the puzzle was Amit Sowani (India). Can be seen as Dutch Snake with orientation given.

Place a snake in the grid. Additionally, the head and tail are defined as H and T. Traveling from H to T, the Snake behaves differently at each letter. It goes straight through all Os. It turns clockwise at all As and anti-clockwise at all Bs.

(Rules and example from WPC 2017 IB)

### Semitransparent Snake

First appeared on WPC 2018/Round 5. Author of the puzzle was Petr Lichý (Czech Rep).

Place a snake. Numbers outside the grid indicate the number of snake cells in that row/column. However, every time the snake goes through 4 or more cells in a straight line, every fourth cell along that line is invisible and is not counted.

(Rules and example from WPC 2018 IB)

### Double Snake

First appeared on WPC 2018/Round 10. Author of the puzzle was Jiří Hrdina (Czech Rep).

Place two snakes. Two snakes can touch each other but cannot overlap except for the given crossings. At the crossings, both snakes must go straight. The heads and tails are given, but their pairing is unknown. The number on the right indicates the number of cells occupied by one snake, and the numbers below indicate the number of cells occupied by one snake.

(Rules and example from WPC 2018 IB. Letters are only for illustrative purpose)

### Easy as Word Snake

Hybrid of Easy as clues and Word Snake. First appeared on WPC 2019. Author of the puzzle was Rainer Biegler (Germany).

"Wortschlange" from Logic Masters 2011 has a similar rule as Word Snake, but outside clues indicate the numbers of vowels in the row.

Rules: Place a snake. The cells of the snake contain the sequence of letters and digits shown below (one character per cell, no spaces). Head and tail of the snake are given. The numbers outside the grid (above and to the left) indicate how many snake cells appear in the respective row or column.

(Rules and example from WPC 2019 IB)