Logic Masters Deutschland e.V.

The rules:

- Place some squares and circles in the grid.
The circles and squares are stations on a network. Connect all the stations together through the center of cells such that no station is isolated from any others. Network lines must travel orthogonally and cannot intersect or cross each other. There must be at least one network line cell between each directly connected station. Square stations must have an even number of network lines emerging from their cells, and circle stations must have an odd number of network lines emerging from their cells.
- The network may comprise dead ends, but any dead end must end in a station. In the network, no circle station may be directly connected to another circle station (circles must be separated from each other by at least one square). Similarly no square station may be directly connected to another square station.
- Cells containing a clue in the corner must contain a station and the number indicates the total number of network cells between that station and all other directly connected stations (excluding the stations themselves). Not all clues are necessarily given.
- Clues outside the grid indicate the number of empty cells in the corresponding row/column (empty cells do not contain stations, or network lines). Grey shading indicates that a cell is empty.

To get solution check, and for the solution code, in each cell where network lines emerge from a station, place the digit corresponding to the number of network lines connecting that station with the next one along that line. For a 2-digit number, place two digits, with the 10s digit in the emerging network cell, and the units digit to its right, if necessary on the station itself, or for column 10 with the 10s digit to the left of the emerging network cell, and the units digit on that cell (see example solution below).