Kids Mode v1.2.0

Everything a kid can reach is now locked down: RetroArch's in-game
shortcuts, the blue-light toggle, and your save states. Plus longer play
sessions, screen brightness from the menu, and a PIN you can change on the
device.

Locked down while armed

• RetroArch's in-game hotkeys are dead — MENU+SELECT (the RetroArch
  menu), MENU+L2/R2 (save/load state), MENU+L/R (rewind, fast-forward),
  MENU+←/→ (save slots), screenshots, cheats, shaders, disc swap and the
  rest. Kiosk mode only ever hid the settings; the menu itself still
  opened. MENU+VOLUME for brightness is untouched — that one is handled
  outside RetroArch. Fixes #4. Prefer stock shortcuts? Set
  "lock_retroarch_hotkeys": false.
• MENU+B blue-light toggle does nothing while armed (a schedule you
  have configured still runs).
• The kid gets their own saves: saves, states and romScreens are
  swapped for a persistent Saves/KidsProfile while armed, so a child
  can't overwrite your save states or flood the game switcher with their
  thumbnails. Their progress persists between sessions; yours comes back
  untouched on unlock. Per-core settings and themes stay shared.

Parent menu

• Longer sessions: the play timer now goes to 120 minutes, up from
  50 — on the arm screen and on Add play time.
• Brightness straight from the menu, changing as you move the row —
  no confirm — in 10% steps down to 10%.
• Change PIN on the device — no computer, no SD card reader.
• Auto-resume last game: boot straight back into what the kid was
  playing instead of the carousel.
• Coming back from a game reopens the carousel on the game just played,
  not at the start.

Carousel

• Battery level on the kid screen, drawn exactly as Onion draws it
  everywhere else (icon and level, top right), with the play-time chip
  opposite it.
• X = RESTART now has a footer hint and icon, so the start-over shortcut
  is visible instead of hidden.
• Long titles wrap onto a second line instead of being cut off with an
  ellipsis.

Faster

Arming went from ~15 seconds of black screen to about 1.5. Three
things were doing it, none of them what they looked like:

• The RetroArch lock matched every setting against every line with a
  regex built from a variable, which busybox awk recompiles each time —
  ~133,000 compilations. Matching each line's key once and looking it up
  in a hash: 14s → under 1s. (It also left duplicate keys later in the
  file untouched, and RetroArch honours the last one, so a repeated key
  silently defeated the lock.)
• Every config read spawned jq. Reads now parse in the shell, with jq
  kept for writes and as a fallback for any file the parser won't touch.
• The timer state file cost three sed processes per read, and the
  ticker reads it every 10 seconds.

Also

• README gains a settings table for kidmode.json and an FAQ (including
  netplay — it's driven from the RetroArch menu, which Kids Mode blocks, so
  it isn't available while armed).
• A kidmode.json with broken JSON is now backed up before being reset,
  so a stray comma doesn't silently lose your settings.

Install

1. Download KidsMode.zip below
2. Copy the KidsMode folder into App/ on your SD card (so it becomes
   /App/KidsMode/)
3. Reboot, then arm from Apps → Kids Mode

Updating from v1.1.0: replace the KidsMode folder — your PIN survives
(it's snapshotted in Saves/kidmode/). The new locks apply the next time
you arm Kids Mode.

Thanks

The hotkey lockout, blue-light guard, save isolation and auto-resume are
@Veuks' work, forwarded by
@andygeorge in #5.

Requires Onion OS 4.3+. Tested on a Miyoo Mini Plus running Onion
4.4-beta; base Mini and Mini V4 are supported in code but less tested —
reports welcome.