Nonogram - A Blender edition

Hello, I try to recreate a Chinese logic game named Nonogram (at least that’s how I know it).

There is an online site for free nonograms, but what I want is to create a Blender game with nice animations, timer and many more features.
You can try the game here:
http://www.puzzle-nonograms.com/
or download it here for Linux users:

What I’ve done so far is this:

I don’t know much about python, but I started taking courses. I have the following issues:

I use Left Click to select a cube (make it black), and Right Click to “forbid” it (make an ‘X’). But I can LC it even if it has an ‘X’ how can I make it non-Left clickable (lol my vocabulary)?

Also for the ‘X’ I use a different object (‘X’ shaped), and as a result I have to bring the mouse over the center to RightClick and at the borders to LeftClick. This isn’t very functionary.

This is an image of the RightClick:


In the future I want to have an inside nonogram creator.
I wait for suggestions, ideas and any other kind of feedback. :eyebrowlift:

Your game is Just great, I think that the logic is working good, really amazing! I think that the structure is set, just a little more work on the design, and it will be great!

Congratulations!