An internet-based pay-once-to-play-forever puzzle game which contains treasure hunt-style puzzles. You can try some sample puzzles at www.thestone.com or www.thestone.net.

As of this writing there are 48 puzzles available on The Stone, but you won't have access to all of them immediately. As you solve puzzles, gradually more are made available to you; in theory, the easier ones are made available first. Players who stick with it eventually catch up and solve most or all of the puzzles available, but they slowly add puzzles over time.

Most of the puzzles have a single word or short phrase for an answer; variations are sometimes accepted, and most puzzles have some "close" answers for which you'll be told you're on the right track.

The puzzles are Javascript-based. A few puzzles use Flash but provide non-Flash versions. Some of the puzzles are multi-part; you'll solve an easier part (like reassembling an image, playing Mastermind or Memory, etc.) and then you'll be given the question you have to answer, or if you were already given it, you'll get a clue. On the other hand, on some puzzles you'll never get a question to answer, but just a set of clues, mostly visual.

Search engines are your friend for The Stone. This is a game that really harnesses the power of the internet, as without it, the amount of research required would probably turn most players away.

There is an overriding theme of mystery, the unexplained, etc. "Time is the answer" is one of their slogans, and this theme often shows up in the puzzles.