Fun

Normal Sudoku rules apply.

Draw a single closed loop that moves orthogonally through cell centers. It must leave exactly nine cells unvisited and visit every other cell exactly once.

The nine unvisited cells contain 1–9 once each, with no two in the same row, column, or box. A cell is unvisited if and only if its digit equals its position within its box.

The loop can be divided into nine consecutive 8-cell sections, each containing eight different digits. The unvisited cell containing a section’s missing digit may not share an edge with any cell in that section.

Normal Sudoku rules apply.

Sequence Thermometers: Digits along each thermometer increase in equal steps from bulb to tip, forming a strictly increasing arithmetic sequence.

The 14 thermometers form seven pairs. Within each pair, the thermometers have identical shapes and bulb-to-tip directions: one can be translated onto the other without rotation or reflection.

The two thermometers in each pair have the same common difference. Different pairs have different common differences.

Normal sudoku rules apply.

Waterline Loop: Draw a single closed loop through cell centres, moving orthogonally. It must visit every non-5 cell exactly once and must not visit any cell containing a 5.

Along each maximal straight segment of the loop, including the turning cells at both ends, the digits must strictly increase or strictly decrease from one end to the other. At each turn, the digit must be either a valley (1-4 and lower than both adjacent digits on the loop) or a peak (6-9 and higher than both adjacent digits on the loop).

Normal sudoku rules apply.

Digits along each thermometer increase in equal steps from bulb to tip. Different thermometers may have different step sizes.

Whenever two thermometers share a cell, exactly one of the two has step size 1.