• Classic Sudoku Each row, column, and 3x3 box must have all the digits 1 to 9 only once.
• Arrow Digits along the Arrow must sum to the number in the circle at the base of the arrow. Digits along the arrow can repeat.
• Ascending Sequences A row should contain the same number of ascending digit sequences as the number to its left, while a column should have the same number of ascending digit sequences as the number above it. An ascending sequences refers to a sequence of cells with numbers that increase from left to right in a row, or from top to bottom in a column.
• Axia A digit in an Axia-marked cell must not appear again along either of the two diagonals extending from that cell. Digits may repeat along diagonals from unmarked cells.
• Between Lines Digits along a Between line must be strictly between the digits in the circles at the ends of the line. Color: Purple-Pink.
• Bishop Digits along each Bishop line cannot repeat.
• Chess King The eight cells directly surrounding a digit cannot contain the same digit.
• Chess Knight A digit cannot be within a Chess Knight’s distance from itself. Chess knight distance is 2 cells over and one cell across in each direction.
• Consecutive Adjacent cells with a hollow rectangle between them must contain consecutive digits. All the other adjacent cells must contain non-consecutive digits.
• Couples Numbers in cells separated by Tilde(~) must have the same parity, either both are even, or both are odd. Numbers in cells separated by Tilde with a slash have a different parity, one must be even and the other odd.
• Diagonal Each digit, 1 to 9, must appear only once on each of the 2 main diagonal lines.
• Dutch Whispers The difference between adjacent digits along a Dutch Whispers line must be at least 4. Color: Orange.
• Even-Odd Cells with a square must contain an even number and cells with a circle must contain an odd number.
• Friendly-Cells Cells marked with a Heart must contain a digit that matches either the row number, column number, or box number.
• German Whispers The difference between adjacent digits along a German Whispers Line must be at least 5. Color: Red.
• Greater-than Adjacent cells must obey any “greater than” (>) or “less than” (<) symbol that appears on their dividing line.
• Index Lookup The digit (X) in a cell with horizontal arrows in column (Y) indicates that, in the same row, the digit (Y) is located in column (X). Vertical arrows follow the same logic for columns.
• Jigsaw Each row, column, and irregular shaped block of 9 cells must have all the digits 1 to 9 only once.
• Killer The sum of the digits in each dotted cage must equal to the number at the top left corner of the cage. Digits cannot repeat in a cage.
• Kropki The digits in adjacent cells with Hollow dot must be consecutive and the digits in adjacent cells with solid dot between them have a ratio of 2:1. Adjacent cells with no dots have no restrictions.
• Little Unique Killer Numbers outside the grid indicate the sum of digits in the direction of the corresponding arrow. Digits cannot repeat within a sum.
• Lockout Lines Digits along a Lockout line must be strictly outside the range of the digits in the squares at the ends of the line. The difference between the digits in the squares at the ends of the line must be at least 4. Color: Light Olive Green.
• Non-consecutive Two horizontal or vertical adjacent cells cannot have consecutive digits.
• Palindrome Digits on each Palindrome line have to be in a symmetrical order, i.e. on a palindrome line, in the length of 5 cells, the following can be a valid sequence: ‘53835’. Color: Light Blue.
• Pulse Orthogonal neighbours of a pulse cell must contain a digit that is adjacent to, a multiple of, or a divisor of the pulse digit. Neither pulse cells nor their orthogonal neighbours may contain the digit 1.
• Quadruple Each digit in the circle must appear at least once in the 4 surrounding cells.
• Reflection Lines are reflections of one another when they have the same starting symbol. Lines with the same symbol have the same digits in the same order, starting at the symbol and onward as long as permitted by the length of the line. Color: Light Apricot.
• Renban Digits on a Renban line must be distinct consecutive numbers, arranged in any order, for example: 3-6-5-4-7. Color: Green.
• Running Cells A row must have the same number of cells with consecutive digits as the number to its left. Similarly, a column must have the same number of cells with consecutive digits as the number above it.
• Sandwich The sum of digits between 1 and 9 in each row must equal to the number to the left of that row. Similarly, the sum of digits between 1 and 9 in each column must equal to the number above that column.
• Skyscraper The numbers around the edges of the grid indicate how many skyscrapers are visible from that vantage point. Taller skyscrapers block the view of shorter ones. Larger digit means a taller skyscraper.
• Slingshot Arrows on the board point from a cell with digit X towards the same digit X, where the digit in the cell of the Arrow indicates how many cells the digit X is away from the arrow, without counting the cell with the arrow itself.
• Slow Thermo Digits along each Slow Thermo line cannot decrease, starting with the smallest digit on the bulb. Color: Pale Green.
• Thermo Digits on a Thermo line must increase, starting from the grey circle.
• Twisted Consecutive Diagonally adjacent cells with a hollow square between them must contain consecutive digits (both diagonals). All other diagonally adjacent cells must contain non-consecutive digits.
• Universal No digit can occupy the same position in any of the nine 3x3 boxes across the entire grid. In other words, each digit must appear in every possible position within the nine classic 3x3 boxes.
• Windoku Each of the four highlighted 3x3 boxes must contain the digits 1 to 9.
• X-Sum The numbers outside the grid indicate the sum of the first X cells from that viewpoint, where X corresponds to the value of the first cell in that direction.
• XV Cells separated by X must sum to 10, and cells separated by V must sum to 5. Adjacent cells without X or V don’t have any restrictions.
• Zipper Line The sum of digits in equal distances from the center of the line equals to the digit in the center of the line. Color: Light Purple.