Basic settings screen functionality has been implemented, including a SettingsView class.
Settings menu works, looks nice, and has good transitions.
Info screen works.
Improved button highlighting, mutable cells highlight green while immutable cells highlight red.
Added sound effect for completing grid.
Highlighting upon choosing an inconsistent value is a work in progress but looking good.
Cleaned up animations when you enter pretty much anything. Added sound effects for entering numbers, erasing numbers, clicking immutable tiles and entering inconsistent numbers.
Updated unit tests and added more.