on and after

Behavior attaches to its owner as an on or after clause inside the owner's create block (or inside a trait). The two words divide one moment: on runs before the action commits and may stop it; after runs once it has happened and reacts.

create the hive box
  aka hive, box
  a thing, scenery, openable
  in the Apiary
  states: humming, quiet

  A white wooden hive box, lid held down by a brick.

  on the player opening
    refuse when the hive box is humming: bees-disturbed
    change the hive box to quiet
  end on

  after the player opening
    phrase honey-smell
  end after

The division is enforced: refuse, refuse when, and must are parse errors inside an after body (parse.react-refusal). If a reaction wants to stop something, it is not a reaction; move it to on. Every clause closes with an end line matching its opener.

The head names who acts

A clause head is actor, then verb: on the player opening. The block it sits in is what is acted on — the hive box above — so the head has one job, naming who is doing it.

create Marguerite
  a person
  starts in the Counting House

  The senior clerk, and she knows it.

create the ledger
  a thing
  in the Counting House

  A ledger, spine cracked.

  on the player taking
    refuse ledger-not-yours
  end on

  after Marguerite taking
    phrase she-checks-the-column
  end after

The two clauses sit on the same object and fire for different people. Write the owner's name where you would once have written it.

the player is a role, not a character

the player means whoever is the player character when the clause fires, so a clause written with it follows the role if the story hands it to someone else. To pin behavior to one particular character instead, write that character's name.

A character's own block needs no name

Inside a person's create block the subject is already settled, so the head drops the actor — the same way wears the boots needs no subject.

create Marguerite
  a person
  starts in the Counting House

  The senior clerk, and she knows it.

  on going
    refuse she-will-not-leave-the-ledger
  end on

That bare head is her own going. Outside a person's block it is an error (analysis.head-bare-outside-actor) — a hive box does not open things, so on opening there has no one to mean.

One head, several actions

When several actions get the same response, list them on one head with commas. The head means one clause per action, each with the same actor, condition, modifiers and body.

create the farmland view
  aka view, meadows, farms
  a thing, scenery
  in the Top of the Post

  The view is spectacular, but you don't have time to waste gawking.

  on the player taking, touching, pushing, pulling, climbing, searching
    refuse view-too-far
  end on

The list works on after heads and bare heads too, and anything after it applies to every action listed: on taking, dropping while the shop is closed, once. Commas are the only separator; taking, touching or pushing is an error that shows the comma form, and an action listed twice on one head is an error at the repeated word. A diagnostic about one of the listed actions points at that word in the list.

Verbs with nothing to act on

Some verbs have no object side, or need none: jump, yes, no, sorry, wave. Each exists in the standard library with a stock line ("You jump on the spot. Nothing comes of it."), and a clause speaks in its place. A verb with no object is written on the room the player is in; a verb with one goes in the thing's block as usual.

create the Landing Pad
  a room
  aka pad, pad 14

  Pad 14 is a circle of old cement under a black sky.

  on the player jumping
    phrase pad-jump
  end on

create the pad master
  a person
  in the Landing Pad
  states: unconvinced, waved-through

  on the player saying_yes while the pad master is unconvinced
    phrase quint-takes-yes-as-the-card
  end on

  on the player saying_no, saying_sorry
    phrase quint-shrugs
  end on

yes, no and sorry go in the block of the person the player is talking to — the clause fires while a conversation with them is live — or on a room, for an answer given to nobody. Inside an open define exchange, yes and no are the exchange's answer and never reach these clauses. Two-word verbs are written with an underscore, as switching_on and taking_off are: saying_yes, saying_no, saying_sorry, looking_under. wave on its own consults the room; wave <thing> consults the thing, which must be held. look under <thing> reveals the concealed things it holds, as search does; empty <thing> spills a container onto the floor, or into another container with empty <thing> into <other>, and both take a clause in the container's block (on the player looking_under, after the player emptying).

A value on the head

set <thing> to <value> carries a word, and a setting head can name it: on the player setting to kepler fires only when that is the value set, and after the player setting with no tail fires for every value. The tail is for setting alone (on the player taking to x is an error naming while <thing> is x as the form for other verbs), and the word must be one of the thing's states.

The other noun on the head

Throwing, giving, showing, putting, inserting, tying and asking for a thing each involve two nouns, and a clause on either one fires. on the player throwing in a bin's block fires for anything thrown at the bin; to say which thing, name it at the end of the head. The clause then fires only when that noun is the one in the command.

create the returns bin
  a container, scenery
  in the Sorting Room

  on the player throwing the dead letter
    move the dead letter to the returns bin
    phrase letter-returned
  end on

create the dead letter
  a thing
  in the returns bin

  on the player throwing at the sorting machine
    phrase machine-spits-letter
  end on

The tail is read from the end of the head. The last the, a or an opens it, and a preposition just before that article (at, for, from, about, in) goes with it; at, for and from open a tail on their own when the name has no article (at Tobias), and giving to Tobias works as you would read it. The preposition is there for reading and changes nothing. A tail goes on a head with one action only, names a thing in the story, and is never the block's own owner; each of those is an error that says so. If a name has an article inside it (the king of the hill), the tail splits at the inner one; refer to the thing by an alias without the article.

There is no word in the body for the other noun: the tail is how a clause names it, and then the body can name it too.

ask <person> for <thing> is its own action, asking_for, separate from ask <person> about <topic>. Nothing is handed over unless a clause does it; with none, the person "doesn't seem inclined to hand over" the thing.

create the pad master
  a person
  in the Landing Pad
  states: unconvinced, waved-through

  on the player asking_for the tram token
    refuse when the pad master is unconvinced: quint-no-token
    move the tram token to the player
    phrase quint-hands-token
  end on

Reacting to a break

A breakable thing can break more than one way: attacking it, and dropping or throwing it when it is also fragile. Each of those fires breaking on the thing after its own line, so one clause in the thing's block reacts to all of them. Its phrase speaks after the action's line, and its body changes the world: sweep up the pieces, spill what was inside.

create the sample jar
  a container, transparent, breakable, fragile
  in the Sorting Room
  states, reversible: sealed, spilled

  after the player breaking
    change the sample jar to spilled
    phrase jar-spills
  end after

Only after works here. By the time breaking fires the thing is already broken, so there is nothing for on to refuse; Chord reports on the player breaking and points you at the clause that can still stop it, on the player attacking (or dropping, or throwing).