This collection of mini-games will appeal to mature gamers looking for a challenge, but only if they can deal with some flawed game mechanics. Zero Escape: The Nonary Games is fantastic for people who want to play a game with tons of puzzles and have their perceptive abilities put to the test. One advantage is that both games are very long. Even if you're doggedly playing, expect a good month or two just to see your first ending in each. The staggering amount of ways where the stories can go down different forks in the road all depend on you, your choices, and what you paid attention to. Since these games are now a few years old, there are countless guides and walkthrough videos online, but cheating to know the solutions robs you of where the game's true strength lies: its variety of puzzles that rely heavily on your observational skills.
Obviously, not all puzzles will be satisfying or fair to all players. The games rely frequently on your ability to memorize each character's plotlines (you'll need to take notes), and also will introduce some mathematical concepts that you'll need mastery of moments later (digital roots, for example). Also, the game's pacing will be fairly polarizing. Play is split into "puzzle" sections and "novel" sections, and were the writing a touch better, the novel sections would be more enjoyable. Both games are frequently overwritten, and also try very hard to seem adult -- too much profanity, too much repetition about drama, and too much casual, juvenile discussion of sex. But both games also have a lot of personality, and they both have genuinely fun and engaging puzzles. Your patience, tolerance, and willingness to endure its shortcomings will obviously vary, but if you're open to a game that will take a long time to learn, a long time to beat, and a long time to see everything, it's worth checking out.