Interaction cost
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Spec: descriptive guidance, not a checkable rule.
It carries no forbidden and instead pair, and no `jig check` detector applies to it directly.
Section: Components and layout

Not a component. A check to run against any flow before calling it finished. See `04-principles.md`, frame 3.

**Count** the clicks, scrolls, pointer distance, keystrokes, waits and things the user must remember or look up.

**Then reduce:**
- Keep the action beside the thing it acts on. Distance is cost (Fitts), and a start-aligned action stays visible to screen magnifier users.
  - A control that closes a panel belongs where the control that opened it was, so the pointer or finger does not travel.
  - Give list and menu items a large, **visibly bounded** target. A border showing the full hit area lets the user be less precise, which is faster.
  - Put a slide-out menu's contents at the top, near its trigger, rather than centred for symmetry.
- Make targets at least `--size-touch-target`. Bigger targets are faster to hit.
- Cut choices, or promote a recommended subset (Hick). Every extra option slows the decision.
- Replace multi-step controls with single-step ones — stepper over select, toggle over dropdown, inline edit over a modal.
- Remove anything competing for attention with the task: banners, autoplay, unsolicited dialogs.

### Reducing choice

Four techniques, in the order to try them (Hick's law):

1. **Remove.** Every option must earn its place. A subscription form asking for first name and company before email is three decisions where one would do — and each field costs completions.
2. **Group or categorise.** Choosing between four categories then four items is faster than choosing from sixteen. Tabs, filters and sections all do this.
3. **Break into steps.** One decision at a time. Long forms become multi-step (`P-04`); large navigation becomes levelled menus.
4. **Recommend.** Where many choices are equivalent, promote the popular ones — suggested searches, a "most chosen" plan, sensible defaults.

**Rule:** when a flow changes, state the before and after counts in one line. "3 clicks + 1 scroll → 2 clicks" is a reviewable claim. "Improved the UX" is not.