Very, very buggy - It is possible to lose inventory with the slightest mistake. And if anyone can tell me EXACTLY how many times to move those levers I would be very grateful, because I just can't get the final piece of circuit board. 2/5
GoogleCZ - I refer you to my earlier comment with the wiki link. You haven't stated that you always start from a solved position when mixing up the pieces. So my comment stands. This puzzle is going to be unsolvable approx 50% of the time. Have you even read my earlier comment and wiki link?
Assuming that the numbers are allocated randomly at the start, then, on average, this puzzle will be unsolvable 50% of the time. Check out this wiki page : http://en.wikipedia.org/wiki/Fifteen_puzzle And check what it says in the first paragraph of the Solvability section.
I liked it - but like other people I wish the pieces would snap into place. I did have a hard time getting some levels to complete. But I did manage to do all 20 in the end.
@Massu1004 : I had the same problem, but it worked okay once I pressed R to restart the level. Then I went up to the ledge on the left, crouched down, and everything worked smoothly from then on.
And when I fail a level and have to "Try Again" - why doesn't it just start the required level again? Instead I have to remember which level I was playing?
 "Puzzles of Gemland"){kind=icon}
 "Unearth"){kind=icon}
 "Fifteen Puzzles"){kind=icon}
 "Mogo-Mogo"){kind=icon}
 "Hinges"){kind=icon}
 "Mystery Jigsaw"){kind=icon}
 "Flash NetHack"){kind=icon}
 "Fortune Hunter: Wrath of Anubis"){kind=icon}
 "Just Chatting"){kind=icon}
 "Hidden Alphabet 12"){kind=icon}
 "Back to the Cubeture (1)"){kind=icon}
 "Wheel It"){kind=icon}
 "Dots and Boxes"){kind=icon}
 "60 Second Crash"){kind=icon}
 "Jungle Magic"){kind=icon}