Plan a bit in the README

01_text_adventure/README.org

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+* Fatal Distractions Chapter 1 - Text Adventures
+** Concept
+I'm not looking for anything super complicated. I've spent maybe 90 minutes
+in my life playing text adventures, I'm sure there are some with really good
+mechanics. For this one, I'm aiming for something at about the level of
+[[https://homestarrunner.com/dungeonman][Thy Dungeonman]]. A map, moving between rooms, getting items, <verb>ing <item>s
+<preposition> <other item>s. If I'm pretty much finished before the end of the
+month, I could add
+ - visual effects
+ - saving and loading
+ - pictures
+ - music
+
+I'm not trying to be a purist about this; I know 99% of all text adventures are
+*just* text, but music is also fun to put together.
+
+** Implementation
+*** Flags
+A flag is a combination name and uinteger value. The value can be changed as the
+result of an action, or checked within a predicate. Three uses for these:
+ - Boolean values, 1 or 0
+ - Countdowns, start at some positive value and eventually become 0 = false
+ - Counters, start at zero and increment ("you have rung the bell 10 times")
+Counters seem really optional, booleans and countdowns seem actually useful.
+Values should evaluate to false if zero, true otherwise.
+Effects should be able to enable (set to 1), disable (set to 0), increment, or
+decrement; if there's need for it, they'll need to set (set to X), I don't think so.
+*** Effects
+When an action evaluates, most of the time it will have no effect ("you can't
+go north from here"). Sometimes though, an action should change the world. Here
+are some effects:
+ - Modify a flag (detailed above)
+ - Change the current room
+ - Add / remove an item from the inventory
+ - Do some meta thing (save or load)
+*** Predicates
+I guess I need a DSL for predicates. I don't think I'll need to implement "OR",
+my predicates should be able to be a chain of clauses "AND"ed together. Some clauses:
+ - IN(room_name), true if the current room has that name
+ - HAS(item_name), true if that item is in the inventory (or in the room)
+ - ENABLED(flag_name), true if that flag has a value > 0
+ - TO(item_name), this is the real tough one, for transitive verbs with an object
+   - 'use key on door'
+   - 'give trinket to dennis'
+   - 'take torch from sconce'
+ Some of these things are items, some are definitely not. Not sure how to codify. Maybe:
+   - DITRANSITIVE(preposition, object), which checks that the command is of the form:
+     <verb> <noun> <preposition> <object>
+ - Even monotransitive verbs ("pull lever") need to specify what they'll act on.
+*** Actions
+Actions are a command, or part of a command, plus a predicate, plus a priority,
+plus a description, plus (optionally) some effects:
+PULL       | *                                      | 1    | You don't see anything to pull |
+PULL       | IN(lever_room)                         | 10   | What do you want to pull? |
+PULL LEVER | IN(lever_room)                         | 100  | You pull the lever. Nice. | ENABLE(lever_pulled)
+PULL LEVER | IN(lever_room) & ENABLED(lever_pulled) | 1000 | You already pulled it.    |
+If the command matches all of the first column, it looks at that action.
+">PULL LEVER" would match all four, ">PULL" would only match the first two.
+The game would choose between all matched actions, filter to only the ones whose
+predicates are fulfilled, and choose from those the one with the highest priority.
+This might require a lot of typing, but I think it will have enough flexibility
+to do everything I might want to do.