Parameter or cue

The range rule: if a sentence cannot stay true across the whole range, the knob should be a cue.

#The rule

If you cannot write a sentence that stays true across the parameter's whole range, it should not be a parameter — it should be a cue.

Both make something change. A parameter hands the change to the reader; a cue keeps it on the author's timeline. The choice is not about which feels more interactive. It is about which claim you are able to make.

#Why the range is the test

A parameter is a claim about its entire range. The moment you declare parameter(var: k; range: [0, 5]) you have promised that the narrative holds anywhere in [0, 5] — because the reader will go there. So the prose has to narrate the space, not a point:

Survives the range: "At degree one the fit misses the curvature; push it past three and it starts memorising the data."
Does not: "The fit passes close to every point" — true at one setting, false at most others.

When only one value supports the sentence, that value is the author's choice, and a cue is how an author's choice is expressed. The rule therefore does something useful beyond tidiness: it forces a document to expose exactly the degrees of freedom its argument covers, and no more.

#Choosing within the cue family

Having decided on a cue, the second question is whether the thing should appear or move:

A mark that should arrive is wrapped — cue{ … }(in: 2).
A value that should change is written with a micronode on the value — x-domain: [0, 5] !cue.to{[0, 10]}(at: 2).
A mark that does both is wrapped and carries a chain.

Anchors & timing covers the anchors and durations both forms share.

#Applying it

The rule is also a diagnostic for documents that already exist. Take each parameter, drag it to both ends, and reread the scene. If the prose is now wrong, you have found either a sentence to rewrite or a parameter that should have been a cue — and the second is far more often the answer.