Zork III Grue Repellant and Ladder Bugs

My wife and I have been playing through Zork III for the first time and we’ve run into a pair of bugs that I haven’t seen documented anywhere so I thought I would share them. We’re playing zork3-r17-s840727.z3 on Windows Frotz 1.25.

  1. We were standing on the Western Shore wearing the cloak. We were able to apply the Grue Repellant to the cloak, then enter the lake, exit to the south, and safely pass through the dark rooms to the Key Room. We didn’t think this was a bug at first, assuming the trick was to apply the repellant to the cloak instead of yourself which would make it last longer. It wasn’t until checking a walkthrough upon discovering the second bug that we learned this wasn’t supposed to work. I have been unable able to reproduce this bug even restoring from a save file in the same game though.
  2. Not knowing that the aqueduct was impassable after the earthquake, we dropped down the manhole and found ourselves trapped. Trying a variety of commands, we found that climb ladder teleported us to the Royal Puzzle Entrance! Thinking surely this was a bug, I looked up a walkthrough and both that and the invisiclues suggests we should have been trapped up there!

    In writing this post, I did some more experimenting and it turns out this works no matter what room you’re in. I was able to teleport from inside the Mirror Box straight to the Royal Puzzle Entrance! After restarting the game, this no longer worked so I assume it only happens after entering and escaping the Royal Puzzle. I scanned the bug list at the-infocom-files/zork3 but didn’t find this called out so thought you all might find it interesting!
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You are perhaps aware of this already, but just in case: the most ambitious collection of Zork III bugs is probably this:
https://github.com/the-infocom-files/zork3/issues

The snag is that if you want to check if your bugs are present in the actual ZIL source code there, you would have to build it yourself, which is non-trivial (but a fun challenge.) Still, it might be worth reporting them there.

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If I understand you correctly, that’s not necessarily a bug. As you say, you have to use the repellent on yourself for it to be effective. The effect wears off after 5 moves.

But even walking around in the dark without the repellent doesn’t necessarily kill you. If I read the source code correctly, walking from one dark room to another has an 85% chance of killing you. Walking into a wall has a 90% chance of killing you.

You have to walk through two dark rooms, but that’s only one move from one dark room to another so it seems you should actually have a not insignificant chance of surviving.

I haven’t tried reproducing it, but CPLADDER is a global object. It’s just that its action routine can print “You can’t see any ladder here.” If I were to guess, you have to solve the Royal Puzzle before you can reproduce the bug? It does check if you and the ladder are in the same Royal Puzzle room, but it doesn’t seem to check that you’re actually in the Royal Puzzle. If that makes any sense.

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If I understand you correctly, that’s not necessarily a bug. As you say, you have to use the repellent on yourself for it to be effective. The effect wears off after 5 moves.

Interesting. Here’s the commands I was entering from the Western Shore:
0. spray can on me
1. enter lake (move to On The Lake)
2. s (move to Southern Shore)
3. s (move to Dark Place 1)
4. s (move to Dark Place 2)

This killed me every time on that last move. The one time I made it through, I used spray can on cloak instead, and it worked! I figured it was because the spray on the cloak doesn’t get washed off in the lake, but then attempting to repeat it never worked again and after seeing the walkthroughs saying I should apply it from the Southern Shore, I chalked it up to a bug. I guess I just got lucky with the 15% chance that time (I figured it was 100% without the repellent).

If I were to guess, you have to solve the Royal Puzzle before you can reproduce the bug?

Seems like it, yeah.