Puzzles are a thorny issue in RPGs. Mainly because they work so very differently than they do in the inspiring fiction. When a character in fiction gets stuck on a puzzle or riddle, it's because the writer needs to build the dramatic tension. When players in a RPG get stuck on a puzzle or riddle it becomes a gridlock situation that rarely leads to anything fun. This is why I avoid puzzles. At least the straight up puzzles. I prefer encounter puzzles. Take a regular encounter. Something the players can use conventional means to solve (skills, abilities, combat powers, etc). Then add a shortcut that can be deduced. For example I recently had a combat encounter with a pair of animated statues and some stone faces with firebolts firing from their eyes attached to a nearby wall. The animated statues were tough and had the ability to immobilize targets they hit, but did minimal damage. The stone faces were easy to hit and damage, but did lots of damage to anything they targeted. The shortcut for the encounter being killing the stone faces first, thus decreasing the damage the encounter inflicted. This was all circumvented by the fact that the animated statues didn't hit the player characters until the 3rdround of combat by which time the players had the statues down to bloodied. This completely illustrates the issue with puzzles. One missing piece of information can cause the whole situation to make no sense at all.