# Crown control experiment (v0.9)

Firmware study of the O63 OTA (`upd_miwear.watch.o63.zip`) found how the crown
reaches quickapps: there is **no crown/rotary JS event** (no `onCrown`,
`onRotary`, wheel keyevents in `vela_quickapp.bin`), but the native layer
(`vela_ap.bin`, `inputmanager/lv_touchpad_wheel_interface.c` + the
`crown_scroll` input tag in `lvx_inputmanager.c`) routes crown rotation into
**scroll deltas of the focused scrollable container**.

So Snake listens to the crown indirectly:

- the page is wrapped in a full-screen vertical `scroll` component with the
  dial centered inside it,
- `onscroll` fires for both crown rotation and finger scroll,
- the page converts each scroll delta into a **queued 90° turn**
  (`snake.rotateDir`, already in the codebase): positive delta =
  clockwise, negative = counterclockwise, `CROWN_STEP_PX` px of scroll per
  turn,
- because turns are 90° relative steps, the crown always turns the snake
  left/right regardless of where the head is pointing, and reversals are
  structurally impossible (rotateDir never emits a 180° flip),
- the scroll position is actively re-centered (`scrollTo({ top: center })`)
  after each event so the board never visually moves; only the idle-swipe
  fallback path (when no scroll events arrive, e.g. some firmwares coalesce
  crown scroll with the swipe handler) uses `onswipe` as before,
- swipes still work exactly as in 0.8; both input paths feed the same
  two-slot turn queue.

Open questions that need the physical watch:

- does the Crown S4 emit scroll deltas with sign, and at what px granularity?
- does `onscroll` fire for crown motion at all on this firmware, or only for
  touch scroll? If not, the `CROWN_STEP_PX` accumulator still catches the
  swipe-path fallback but true crown control would need native access.