A game unlike anything else I've played. A brilliant story backed by solid gameplay; great characters, art music, sound.
Sometimes the gameplay has a bit of trial-and-error, but the characters will often say things that helped you. But in a way, it's much of the fun of the game. Think of something that might help, then manipulate things differently, and see the result. I fell back on a walkthrough once or twice, and in retrospect the solutions were obvious. Completely fair puzzles, even the ones that involve timing. You have as many "retries" as you need, but that doesn't make it "easy. Sometimes getting a solution will make you feel like a genius. It is rewarding.
The core mechanic of manipulating objects doesn't change for most of the game, but it doesn't need to. The game throws you in different environments with different items and different objectives. (Although many involve preventing a death, the method still varies.)
Neither story nor gameplay ever bored me for all of the 10+ hours of playtime. (I had a hard time putting the game down.)