Hashi (Hashiwokakero) also known as Bridges is a logic puzzle with simple rules and challenging solutions.
The rules are simple.
Hashi is played on a rectangular grid with no standard size. Some cells start out with numbers from 1 to 8 inclusive; these are the islands. The rest of the cells are empty.
The goal is to connect all of the islands into a single connected group by drawing a series of bridges between the islands. The bridges must follow certain criteria:
They must begin and end at distinct islands, travelling a straight line in between;
They must not cross any other bridges or islands;
They may only run orthogonally;
At most two bridges connect a pair of islands; and
The number of bridges connected to each island must match the number on that island.
Left click an island and drag toward another island. Release the mouse when both islands are highlighted.