Apps describe nesting instead of coordinates: /lib/ui.lua borrows CSS block flow,
the box model and auto sizing, and owns hit testing, press capture and the pressed
repaint. The runtime gains require backed by the SD card, on_touch_down/on_touch_up,
text metrics and rounded gradient fills, so the launcher becomes an ordinary Lua app
and the firmware keeps only a fallback screen for an unreadable card.
Boots to a launcher that lists /apps/<name>/main.lua on the SD card and runs
the selected app in a vendored Lua 5.4 with gui, input, fs, sys and log
bindings. Settings persist as a Lua table in /settings.lua, covering touch
calibration and screen rotation, with a settings app to edit both. Rotation is
applied after mapping raw touch into the panel's rotation-0 frame, so turning
the UI never invalidates a calibration.
evan