1. Thermometers Sudoku (Arvid Baars) The digits in each thermometer-shaped region should be in increasing order, from the bulb to the end.
2. Search Nine Sudoku (Richard Stolk) Every arrow is pointing at number 9 in the respective row or column. The number in the arrow is the distance (with respect to the number of cells) from the arrow to the 9.
3. Quad Max Sudoku (Arvid Baars) An arrow in a circle points to the highest digit in the four neighbouring cell
4. Odd Max Sudoku (Richard Stolk) A digit in a circle appears exactly one time in the four surrounding cells and it is the highest odd digit in those four cells.
5. Toroidal Bricks Sudoku (Arvid Baars) In the grid stones of size 2x1 are placed. Every stone contains one odd and one even digit. Some stones wrap around the grid from left to right.
6. Rank Sudoku (Richard Stolk) A digit X in a circle means that the digit in the cell is the X-th smallest number in the corresponding cage. Digits cannot repeat within a cage.
7. Treasure Hunt Sudoku (Arvid Baars) Place the digits from 1 to 9 in every row, column and boldly outlined irregular area. A digit in a circle tells the number of treasures in all the cells directly around it. A treasure is a digit that is higher than the digit in the circle.
8. Next to Nine Sudoku (Richard Stolk) Digits outside the grid are the direct neighbours of the nine in the respective row or column.
9. Diagonal Kropki Sudoku (Arvid Baars) A black bar between two diagonal neighbouring cells means one of the digits has the double value of the other digit. A white bar between two diagonal neighbouring cells means one of the digits is one higher than the other digit. If there is no bar between two diagonal touching cells, none of these constraints is true.
10. Sudoku Plus Minus (Richard Stolk) The digit in a circle on a vertical line is the sum of digits above and below it. The digit in a circle on a horizontal line is the difference between the digits on its left and on its right.
11. Star Battle Sudoku (Arvid Baars) Place the digits from 1 to 9 in every row, column and boldly outlined area. Two of these nine digits are "stars"; so there will be two stars in every row, column and boldly outlined area. Stars don t touch each other, not even diagonally. You have to find out yourself which digits have to be replaced by stars.
12. Consecutive Sandwich Sudoku (Richard Stolk) All the digits that are written outside the grid have two neighbours that are one higher and one lower than the digit itself in the respective row or column. Digits that are not written outside the grid don t have two of such neighbours.
13. Pinocchio Sudoku (Arvid Baars) Place the digits from 1 to 9 in every row, column and boldly outlined irregular area. There are three numbers written in a different lay out. Two of these numbers are correct, while the third one is the lying Pinocchio. Find out which number is incorrect and solve the puzzle as a standard irregular sudoku.
14. Outside Twin Killer Sudoku (Richard Stolk) Place the digits from 1 to 9 in every row, column and 3x3-block of both grids. Replace the question marks in each dotted outlined area with a number that is written on the left of the corresponding row. After that, the small numbers in the dotted outlined areas are the sum of the digits in that area. Within a dotted outlined area all digits must be different. Both grids have the same solution
15. No Three in a Row Sudoku (Arvid Baars) In this puzzle there is a restriction on the number of odd/even neighbouring digits. The maximum number of neighbouring odd digits as well as the maximum number of neighbouring even digits in any row or column is two.
16. Between Sudoku (Richard Stolk) Digits on each line must be between the digits in the circles at both ends of the line.
17. 2358 Difference Sudoku (Arvid Baars) A small digit 2, 3, 5 or 8 between two cells means that the difference between the two digits is 2, 3, 5 or 8. Beware: Not all differences 2, 3, 5 and 8 are given
18. Greater Than Consecutive Sudoku (Richard Stolk) In all cases where the difference between two neighbouring digits is 1, there is a greater or less sign between those digits. Digits must be placed in accordance with the signs.
19. Sequence Roundabout Sudoku (Arvid Baars) Around every arrow in the grid there is an arithmetic sequence of 3 or 4 numbers. The numbers that are part of the sequence have the same differences between them. Valid sequences could be 1-2-3 or 2-4-6-8 or 1-5-9 or 3-6-9. 1-2-4-8 is not a valid sequence. Sequences start with the lowest number, going clockwise or anticlockwise as indicated by the arrow. If there is no arrow, there can t be a sequence.
20. Maximum Triplet Sudoku (Richard Stolk) In every row and column there is at least one triplet (three horizontally/ vertically connected cells) of which the sum is given outside the grid. At the same time, these sums are the maximum sum of any triplet in the respective row or column
21. City Construction Sudoku (Arvid Baars) Place all buildings in the grid. Buildings may be rotated and mirrored. They may not touch each other, not even diagonally. All unused cells form a single, closed loop. None of the buildings may be placed on a digit that is already given in the grid.
22. Rhombus Sudoku (Richard Stolk) There are some rhombus shaped figures in the grid. The sum of numbers on the rhombus vertices should be divisible by the central number. (The number inside the rhombus).
23. Domino Sudoku (Arvid Baars) Place all the given dominos exactly once in the dotted white 2x1-shapes in the sudoku grid. In the grey shapes 4 different dominos appear for a second time.
24. Clone Sudoku (Richard Stolk) The grid contains five different shapes. Each shape is cloned one or more times. Cloned shapes may be rotated, but the position of the digits within them remains fixed. Within a single shape, no two digits are the same.