This version of the Locked Door series (which adds more and more puzzles to the original) introduces the first real puzzle, although its fairly simple.
Rather than the original two rooms, there are now 5, with one room included in another.
There was a bug in this one, where trying to (Spoiler - click to show)open the crate without (Spoiler - click to show)the crowbar will (Spoiler - click to show)increase the score and partially act like you have the crowbar but not open. Given the smallness of the game, I think it could have been error-free.