I was a senior in college when this game was released and played it the moment it dropped. I took copious notes while playing and brought those notes to my classes, occasionally ignoring my professors to hammer out this puzzle. No regrets.
The conceit--building a dungeon worth of death traps as a contract to hire for a perverse king--is brilliant. Despite the dungeon having 16 rooms and there being 17 traps to purchase, there is only one solution to killing off the prisoner; as such, Lock & Key more than any interactive fiction feels like solving a logic grid puzzle from a games magazine. As the prisoner continually foils traps, you must determine what traps are completely worthless versus what traps slow him down (and in the best order they slow him down).
Naturally, there is much "learn by dying" as you take notes on why each traps fails and why. And, unfortunately, every time the prisoner escapes you have to start over from scratch. So every play through involves a tedious resetting of doors and resetting of traps. There are some shortcuts implemented to tackle this and if you are confident in your door layout or some of the trap layout you can create a save file to save you some time. But even while taking advantage of both, I was beginning to resent the game a little before I solved it, which in turn took some of the joy out of the triumph.
If you're a fan of dark, witty humor (which a game like this requires in order to be palatable) Cadre provides plenty with nearly every possible action. It certainly takes a little bit of the edge off the tedium.