SD Snatcher. It has some wonderful simple dungeons but there is also one big example how not to design one.
This puzzle consist fact that there is about at least dozen candles and you are expected to blow them all out so the door can be opened in the end of the said puzzle area. Should you miss any, guys in the almost at the puzzle's end point out that you must blow them all out. Causing player to potentially go back a long way because he even didn't knew about the puzzle yet.http://lparchive.org/SD-Snatcher/Update%2019/