Light Up

Light Up

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

You're on a rectangular grid and you have to light up all the cells. For that, you need to put some lights in dark cells (so no light should illuminate another). The lights that you have illuminate in the four directions from wall to wall. And there are constraints: some walls must have a given number of lights close to them.

The grid will be represented by a tuple of strings. Cells that are in the dark will be represented by ' ', walls by 'X' and numbers '0', '1', '2', '3' and '4'.

You have to return the coordinates of all the lights you want to place to illuminate the entire grid.

7x7 example image

Possible lights: [(0, 5), (5, 6), (3, 3), (4, 4), (0, 0), (2, 2),
                  (6, 5), (6, 1), (5, 0), (1, 1), (1, 6)]

('    1  ',
 '   0X  ',
 'X2     ',
 ' 0   0 ',
 '     11',
 '  X0   ',
 '  1    ')

Input: A tuple of strings.

Output: An iterable of tuples/lists of two integers.


list(checkio(('    1  ',
              '   0X  ',
              'X2     ',
              ' 0   0 ',
              '     11',
              '  X0   ',
              '  1    '))) = [(0, 5), (5, 6), (3, 3), (4, 4), (0, 0), (2, 2),
                              (6, 5), (6, 1), (5, 0), (1, 1), (1, 6)]

To play the puzzles / tests yourself: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15


  • Given puzzles are solvable and there is only one solution (when the coordinates are sorted).
  • 7 ≤ len(grid) ≤ 50 and 7 ≤ len(grid[0]) ≤ 60.
  • all(len(row) == len(grid[0]) for row in grid).

Invalid hot key. Each hot key should be unique and valid
Hot keys:
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.

Pair Programming (Beta-version)

Welcome to Pair Programming! Engage in real-time collaboration on coding projects by starting a session and sharing the provided unique URL with friends or colleagues. This feature is perfect for joint project development, debugging, or learning new skills together. Simply click 'Start Session' to begin your collaborative coding journey!

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Please wait for the session creator to join.

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It might happen accidentally, so that you can wait for reconnection.

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