Thanks for the feedback! I hope you enjoyed playing with it.
And you're right - it is quite easy to get stuck and have to guess. I've toyed with permitting a single "free click" or "reveal non-lethal square" option, but haven't figured out what would help. Your suggestion of "two lying squares cannot touch" would be pretty easy to implement, I believe, and could lead to another step in the deduction...
And - again - thanks!