Futoshiki is a logic puzzle game from Japan. It is also spelled hutosiki (using Kunrei-shiki romanization). The puzzle is played on a square grid, such as 9 x 9. The objective is to place the numbers 1 to 9 (or whatever the dimensions are) such that each row, and column contains each of the digits 1 to 9. Some digits may be given at the start. In addition, inequality constraints are also initially specified between some of the squares, such that one must be higher or lower than its neighbour. These constraints must be honoured as the grid is filled out.

Straights is a logic puzzle. It is a grid, partially divided by black cells into compartments. Each compartment, vertically or horizontally, must contain a straight - a set of consecutive numbers, but in any order (for example: 2-1-3-4). The aim is to fill all white cells with the numbers from 1 to N (where N is the size of the grid). No single number can repeat in any row or column. Clues in black cells remove that number as an option in that row and column, and are not part of any straight.

Suguru ("Number Blocks") is a logic puzzle invented by Naoki Inaba (Japan) that has simple rules, but which provides sufficient challenges to satisfy the most enthusiastic solvers . The task consists of a rectangular or square grid divided into regions. Each region must be filled with each of the digits from 1 to the number of cells in the region. Cells with the same digits must not be orthogonally or diagonally adjacent. Even though the rules are simple, you will need all your skills to solve it.