Constraint Satisfaction

A classic sliding puzzle: fifteen numbered tiles and one blank in a 4×4 frame; slide tiles into the blank until they read 1–15 in order.

A Nikoli logic puzzle: place bulbs so every white cell is lit, no bulbs shine on each other, and numbered walls have the required adjacent bulbs.

A two-symbol puzzle: on an even-sized grid, place 0s and 1s so each row and column has equal counts of each, no three identical symbols run consecutively, and no two rows or columns are identical.

A mechanical puzzle of linked rings on a handled bar: following two simple rules, take the rings off one by one, or put them back on. The classic nine-ring set takes hundreds of moves.

An inequality puzzle: fill an n×n grid with 1–n so no digit repeats in any row or column, and every > or < sign between neighbors holds.

A bridge puzzle: connect numbered islands with horizontal or vertical bridges so each island has as many bridges as its number. Two islands share at most two bridges, bridges never cross, and all islands must link up.

A room-shading puzzle: shade cells in bold rooms so each number matches its room’s shaded count. Shaded cells can’t touch side by side, white cells stay connected, and a straight line of white cells spans at most two rooms.

Fit irregular, usually interlocking pieces together to rebuild a complete picture and outline.

Shade cells so the column numbers of shaded cells in each row, and the row numbers in each column, add up to the given clues.

A logic puzzle: fill white cells with digits 1–9 so each crossword-like run matches its clue sum and contains no repeated digit.

An arithmetic puzzle: fill an n×n grid with 1–n so no digit repeats in any row or column, and the numbers in each thick cage reach its target with the given +, −, ×, or ÷.

Shade cells so each number equals the white cells it can see in four directions, itself included; shaded cells can’t touch, and whites stay connected.

Press a light to toggle it and its four neighbors; the goal is to turn every light off. The classic board is 5×5.

A 3D interlocking wood (burr) puzzle: notched sticks assemble into a rigid cross without glue; take apart and reassemble.

A two-player code-breaking game: guess a hidden row of colored pegs; black keys mark right color and place, white keys mark right color wrong place.

A pearl loop puzzle: draw one simple loop through cell centers that visits every white and black circle, obeying straight/turn rules that differ by color.

A picture logic puzzle: paint cells filled or blank so every row and column's contiguous blocks match the edge run-length clues—often revealing a hidden image.

A shading logic puzzle: form numbered white islands of exact size while painting one connected black wall with no 2×2 black pools.