* Rework the Story Mode UI to display level thumbnails.
* Responsive UI: defaults to wide screen mode and shows 3 levels horizontally
but on narrow/mobile display, shows 2 levels per page in portrait.
* Add "Tiny" screenshot size (224x126) to fit the Story Mode UI.
* Make the pager buttons bigger and more touchable.
* Maximize the game window on startup unless the -w option with a specific
window resolution is provided.
* Build the app with -tags="shareware" to compile the free/shareware
build of the game.
* `make build-free` compiles both binaries to the bin/ folder in
shareware mode.
* The constant balance.FreeVersion is true in the shareware build and
all functionality related to the Doodad Editor UI mode is disabled
in this build mode.
