Net Game Net Game
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This mission is an adaptation of the "Net" game (from Simon Tatham's Portable Puzzle Collection ). If you are lost or just want to play, the game is available here .

You have a rectangular grid with tiles you can only rotate, but it's a bit messy: tiles aren’t connected like they are supposed to be. You’ll have to put them in order by rotating each tile to reassemble the network .

The successful solution will be an entirely connected network with no closed loops.

There are four types of tiles:

  • Dead ends W
  • Straight roads NS
  • 90° turns NE
  • T junctions WSE

Tiles will be schematized by the directions to which they point ( N orth, W est, S outh, E ast), and more precisely with a string of directions (for example 'NE' if the tile is pointing to the Northeast, then it's a 90° turn).

Note that the order of directions in the string is meaningless (for example: 'NSE' and 'ENS' are the same) for input and output.

5x5 example: input and output images.

[['NW' , 'S'  , 'N'  , 'E'  , 'SE'],       [['SE' , 'W'  , 'S'  , 'E'  , 'SW'],
 ['NS' , 'W'  , 'NWE', 'NWE', 'SE'],        ['NS' , 'S'  , 'NSE', 'WSE', 'NW'],
 ['WSE', 'NSE', 'NWE', 'W'  , 'E' ],  ===\  ['NSE', 'NWE', 'NWS', 'N'  , 'S' ],
 ['WE' , 'WS' , 'WSE', 'SE' , 'WE'],  ===/  ['NS' , 'SE' , 'NWE', 'SW' , 'NS'],
 ['W'  , 'NE' , 'N'  , 'NW' , 'WS']]        ['N'  , 'NE' , 'W'  , 'NE' , 'NW']]

Input: A list of lists of strings.

Output: A list/tuple of lists/tuples of strings.


checkio([['NW' , 'S'  , 'N'  , 'E'  , 'SE'],
         ['NS' , 'W'  , 'NWE', 'NWE', 'SE'],
         ['WSE', 'NSE', 'NWE', 'W'  , 'E' ],
         ['WE' , 'WS' , 'WSE', 'SE' , 'WE'],
         ['W'  , 'NE' , 'N'  , 'NW' , 'WS']]) == [['SE' , 'W'  , 'S'  , 'E'  , 'SW'],
                                                  ['NS' , 'S'  , 'NSE', 'WSE', 'NW'],
                                                  ['NSE', 'NWE', 'NWS', 'N'  , 'S' ],
                                                  ['NS' , 'SE' , 'NWE', 'SW' , 'NS'],
                                                  ['N'  , 'NE' , 'W'  , 'NE' , 'NW']]

To play the puzzles / tests yourself: 1 2 3 4 5 6 7 8 9 10 11 12


  • Given puzzles are solvable.
  • 3 ≤ len(grid) ≤ 25, 3 ≤ len(grid[0]) ≤ 40.
  • all(len(row) == len(grid[0]) for row in grid).

CheckiO Extensions

CheckiO Extensions allow you to use local files to solve missions. More info in a blog post.

In order to install CheckiO client you'll need installed Python (version at least 3.8)

Install CheckiO Client first:

pip3 install checkio_client

Configure your tool

checkio --domain=py config --key=

Sync solutions into your local folder

checkio sync

(in beta testing) Launch local server so your browser can use it and sync solution between local file end extension on the fly. (doesn't work for safari)

checkio serv -d

Alternatevly, you can install Chrome extension or FF addon

checkio install-plugin
checkio install-plugin --ff
checkio install-plugin --chromium

Read more here about other functionality that the checkio client provides. Feel free to submit an issue in case of any difficulties.

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