Stostone Rules

Stostone is a new puzzle type by Nikoli. Shade exactly one stone, a connected group of cells, in each region, such that no two stones in different regions are adjacent. If a number is in a region, it tells the size of that region’s stone. If you let the stones all fall down, they must cover exactly the bottom half of the grid.

See the example below, where the 1st grid is the puzzle, the 2nd grid is the solution, and the 3rd grid is what it looks like if all the stones fall down.


Pentominous Rules

Divide the grid into pentominoes such that no two pentominoes of the same shape are touching at a side. There will be some letters in the grid, that tell which shapes they belong. The 12 pentominoes and their names are given below. Notice that the pentominoes are still considered the same shape after being rotated and/or reflected.


Heteromino Rules

Draw lines to divide the white squares into groups of three, such that no two identical groups that are also at the same angle are touching at a side. See the example puzzle below on the left. The correct answer is in the middle, and an incorrect answer is on the right, because the two triominos that are at the same angle in red are touching.



Snake Rules

Rules: Locate a snake in the grid, whose head and tail are given.The snake must only move parallel to the grid lines, and go through centers of grid cells. The snake does not visit squares which touch those it has already visited, either adjacently or diagonally. Numbers outside the grid indicate the number of cells in that row/column that the snake goes through. See the example below:



Anglers Rules

The fishes shown in the lake are such that every angler (numbers on the periphery) gets exactly one fish. The numbers indicate the length of the fishlines. Draw the fishlines starting from grid border such that no two of them cross or overlap each other. Generally, every square will be used.



Nurikabe Rules

The object of nurikabe is to shade some cells to create islands  so that the number of squares in each island is equal to the value of the clue, the wall form be in one connected part  and there are no wall areas of 2×2 or larger. Each island must contain exactly one clue and no two islands can touch. See the example below for any clarification.



International Borders Rules

The object is to shade in some of the grid squares without circles so that the grid is partitioned into a number of regions equal to the number of colors (besides gray) in the grid. Any two circles of the same color should have a path between them through adjacent, unfilled squares, but no two circles of different colors should have such a path. If a circle has a number inside of it, that tells how many of the four adjacent squares are filled in. Finally, there can be no “useless” filled squares that do nothing to separate the regions. More precisely, any filled square must be adjacent to at least two different regions.

If you are confused, see the example below:


Right Face Rules

Right Face is a puzzle made by Palmer Mebane, and many of the rules are paraphrased or taken from his blog at A robot begins on the square marked with a red arrow, facing in the arrow’s direction. It will proceed forward until the square ahead of it is a wall or one it has visited before. When that happens, it will first try to turn right (hence the puzzle name) and proceed forward. If the square ahead of it is still a wall or one it has visited before, it will go back and try to turn left instead. If it cannot do that either, it stops. The object is to determine which of the grid squares are walls such that the robot visits every grid square not marked as a wall before stopping. Some objects in the grid are given. Black boxes represent walls given to you. Black dots represent squares that cannot have a wall. Arrows also cannot have walls, and additionally when the robot steps on the arrow it must travel in the arrow’s direction on its next move. Note that this is a condition on you, not the robot. The robot will proceed with the instructions in the first paragraph regardless of the square, and it’s up to you to make it move in the right direction on arrowed squares. In particular the robot’s first step from the red arrow must be forward. Finally, the robot’s path must end on a square with a dot.  In a puzzle in which no red arrow is given, one of the black arrows should have actually been made red. It is up to you to figure out which one.

See the sample puzzle below for any clarifications, or ask in the comments if you are confused


Double Back Rules

 The object is to draw a single closed loop passing through every cell in the grid. The loop must enter and exit each contiguous region exactly two times. 

Wow, the rules are surprisingly short. If I happened to leave something out, see the sample puzzle below.