Renga in Blue   Interactive fiction and the All the Adventures project

(Previous posts on The Paradise Threat here.)

This is, without question, one of the worst parsers I have dealt with in a long time, and that includes all the other Pearson games. I had numerous points where I knew what I wanted but couldn’t communicate, or where I wasn’t sure if I was doing the right thing.

First off, a little theory. I’m going to explain how the “rulebook sequence” in the parser for Inform 7 works (which is as modern as it gets) just to give a sense about the problem of message priority. From the Inform 7 handbook:

First it makes sure it knows what the input words are, and that the command makes grammatical sense … If there’s a typo in the input — or even if the parser knows all of the individual words but doesn’t understand how they’re strung together — the parser will reject the input before anything happens. Assuming the parser can figure out what the words are, and that they’re in a grammatical form that the parser knows, Inform starts processing the action.

The game then checks Scope to see if your item being referred to can be seen (or if it is a case where it makes sense to refer to something even if you can’

>open gate
You can’t see any such thing.

(You also get the same message if you try a noun that isn’t in the vocabulary — the game is trying to prevent “noun hacking” here to find objects that you haven’t seen yet.)

Once past that phase, things get more complicated:

There’s a Before section, which is checked before anything else. This triggers before any checking of the world environment, so this is for responses that override even checking if an action is plausible; it just checks if a verb is trying to be used. Suppose the player tries EAT CHEESE. A player controlling an alien with no mouth might just immediately be told they have improper anatomy; even if the cheese is in a locked container, it is much more logical to just say the action will never work.

The game then passes through an Accessibility check; even if the target of an action is “in the room” with the player it might be impossible to reach. So here is when EAT CHEESE might inform the player that the cheese is locked away and you don’t have any way of getting at it.

This is followed by an Implicit action check. This accounts for circumstances where the player expects item-juggling to be handled automatically, like unlocking a door with a key that is held in one’s pocket; the game can automatically take the key out of the pocket rather than force the extra steps, and will be explicit about this happening with a message like “(first taking the key out of your pocket)”. In the cheese-eating instance, if the cheese is close enough to reach, the game might have the player first pick it up before eating it.

Then comes the rulebooks Instead, Check, and Carry out. This is the “central” part of the parser and includes more specific checks like the cheese you’re eating is really a rock (which you find out by trying to eat it). Finally there’s an After section (there might be a chain reaction of other things after successfully eating the cheese, for instance).

This structure has been designed after a lot of experience with parsers having strange messages because of priority issues. Not every condition has been obvious. If you try to EAT PRIME MINISTER and there isn’t a single government official in sight (perhaps the Prime Minister walked to a different room and the player didn’t notice), the best response is to say you don’t see the Prime Minister, not “don’t be a cannibal”. The cannibal message feels appropriate but implies the Prime Minister is visible; the player then may try to GIVE LETTER TO PRIME MINISTER and be confused.

The Paradise Threat has (in addition to other parser sins I’ll get into) some priority issues. Suppose, having seen some timber described you try to GET TIMBER and you’re holding six items. The game will go

ONLY SIX ITEMS PLEASE.

This implies “you’d be fine getting it, but only if you reduce your inventory”. So you do some item juggling and try to get the timber now, getting

IT’S NOT A VISIBLE ITEM.

Clearly, the fact that the timber is not considered “visible” is the more salient fact than the player’s inventory capacity. The game is essentially checking conditions in the wrong order.

I’ll hit other issues in context, let’s get back to the action–

Last time I had dropped off a wood box to get consumed by termites but couldn’t get at the result. I waited around a very long time and nothing happened. I had neglected one of the other Pearson tendencies: to have time pass based on entering certain locations. That is, in most games, if you have a timed event, you might think to type WAIT sufficient times and the game will move on; in the case of The Paradise Threat, sometimes you can hang out for many turns and find nothing will ever happen. The game is waiting for you to move to some other specific part of the map, and passing throw room X will cause the time-passing condition to happen in the earlier room Y.

I went over to the arrow-killing room, stepped back out (as long as you immediately go west you don’t die) and then found the termites were finally done with their snack.

The packet had seeds, so I took them to the soft area I was able to dig. After PLANT SEEDS I had to walk around a bit more; the “arrow-killing time pass” seemed to do the trick again.

There’s a cliff described as also being at 30 feet, so you have to wait around for the plant to get that high.

Before showing the result, I should mention I elided something important on the parser: PLANT SEEDS. PLANT is not understood as a standard verb elsewhere. Hence it turns out that this is a game with a “standard dictionary” of verbs and response to when they don’t work, but also a bespoke set of verbs-with-nouns that will work only in the particular cases they are intended. In that parser diagram, you have to imagine a brand-new list of phrases which all get interpreted on their own outside of the main structure.

PULL, which I originally thought didn’t work, works specifically here: you can PULL ROPE to get the crossbow to launch early.

TWAANNG…..THUMP !

This disarms the trap that had been stumping me. Looping back around to the trap and the next room:

If you just drop the scepter it disappears. The logical step to me seemed to be to attach the ivy to the scepter, but I went through

TIE IVY VINE
ATTACH IVY VINE
WRAP IVY VINE
ATTACH SCEPTER
PUT IVY VINE

and many other permutations before arriving at the exact phrase TIE IVY VINE TO SCEPTER. This is the only way to do the operation. TIE IVY VINE along just gets “I DON’T UNDERSTAND”; trying to TIE IVY VINE TO SCEPTER while anywhere other than this specific room also gets “I DON’T UNDERSTAND.” This is about as mind-bogglingly misleading as a parser message can be, especially because it isn’t playing guess-the-verb, it’s playing guess the phrase.

Essentially, the “bespoke phrase” part of the parser skips any of the kinds of checks a good parser might have and only looks for: are you in the right room with the items, and have you typed the exact phrasing? If so, go on, otherwise, go to the generic non-understanding message.

You have to incidentally JUMP to get back (both JUMP VINE and JUMP IVY VINE work; the game inconsistently will sometimes need the two-word version of the noun and sometimes not). This reflects one of the other issues with the game, that map traversal requires very specific phrasing and reversing directions isn’t consistent. Normally, when outside a cave with steps, even our lower-tier parser games would accept at least a subset of GO CAVE, U, E, ENTER CAVE, GO STEPS; you have to CLIMB STEPS exactly. Trying to CLIMB STEPS to go back has the game say

YOU’LL FALL.

being of course the exact same steps we just climbed up. No, you have to go WEST to go backwards. I have to essentially glance at my map every time I pass back and forth to make sure I’m typing in the right word. Door to the east? OPEN DOOR, not EAST. Going back, OPEN DOOR fails — “you can’t” — and you go WEST instead.

Once in the hall, the game takes a moment to go meta.

ANSWER PHONE:

However, trying to make the conversation go further I was stumped; LISTEN gave me I HEAR NOTHING COMPREHENSIBLE; trying to ANSWER the phone again did as well. I assumed I was in another part of the game which required exact phrasing, so I ran through about 30 phrases before looking at the phone, which (after what looks like a cut-off conversation) has a tiny key.

Moving along…

From Lucifer’s Realm.

…I came across a Nazi guard at a door. Trying to KILL GUARD (we have a sword, after all) gets

YOU’RE TOO KIND.

which is the default “kill but not understood” response. If you TALK GUARD…

…only then do you have the opportunity to KILL GUARD and finally be understood. However, the guard just blasts you with his gun.

Being stuck I let the death happen, since that just warps you to the start, and explored around a little, keeping in mind Pearson was going full steam now on the “timed events” that were really dependent on you reaching some farther location.

As typical, it took an infuriatingly long time to figure out how to get into the hole (CLIMB HOLE) and then you just find out it is a latrine. The smell is enough to kill the guard if you go for a round 2.

We’re about to see a bunch of Nazis and none of them have this reaction.

Heading past, you get into a “huge hall” and a “reception room”. Taking the reception room first, we are encouraged to come back later, which sounds like another “timed” event to me.

There’s food on a tray we can access, so I assume he hasn’t actually started lunch yet.

Back in the huge hall, I did a LOOK HALL and found some lumber. LOOK LUMBER reveals a board.

Yet again I had enormous parser struggles, finally landing on PULL.

The board seems like it’d help with the quicksand, but no dice. I tried about 30 different parser commands, gave up, and went to check if Will had already gotten that far in his first writeup.

That’s not the case but moving on I find that I can indeed drop the board and thus access the quicksand room without sinking. I can thus reach the pillar and pick up some powder.

DROP BOARD, then go EAST? Nope. Drop board before arriving in the quicksand room, then going east? Nope. Not

CROSS BOARD
STAND ON BOARD
STEP ON BOARD
WALK ACROSS BOARD
USE BOARD
GO TO PILLAR

etc. etc. etc. etc. etc. etc. Still no idea what to type even though I’m following Will’s exact directions.

We’re mostly past this nonsense in 1982; the only parser from that year of comparable badness I remember is Grandell Island. What’s so baffling here is I certainly don’t remember this much trouble from the prior Pearson games. I think the author is trying hard to make a “compact” game where every step is interesting but the end result is that every step I can only manage on the fourth or fifth parser attempt.