Lure of the Labyrinth. The interesting part of this game is that it has a separate 'Play the Puzzle' section; the link is just under the 'Play the Game' legend.
If you're not really into playing long games, you can just play the puzzles. You won't get any game credits by playing the puzzles outside of the main game, but they are fun on their own!
You must sign up to play either the game or puzzles but logging in is immediate, with no hunting around for a confirmation email. Click "Sign up here!", create a username and password and off you go!
And let me know if you prefer the game or the puzzles.