The first half of Nibiru is the strongest with many obstacles to overcome in Prague, and then just getting access to the tunnel is an extended puzzle in itself. Once in the tunnel the mystery deepens and some answers are gradually revealed as you explore. The Paris interlude before Martin sets off for Mexico didn't work as well for me as it tended to break up the flow of the game and I couldn't understand why Martin didn't just stay in one of the many rooms of his uncle's mansion instead of fiddling about in an hotel. Ok, it was necessary to the plot, but it might have been handled better. The last part of the game in Mexico involving the Mayan temples returns to much firmer ground although the enigmatic ending left me a little bemused. Overall Nibiru is an intriguing and entertaining game, not overly difficult, and I had a lot of fun playing it.