Principia uses a directory to store settings and levels. Sometimes you would want to access this to manage and backup your local levels, or to check the game logs.
1.5.1 and prior:
/storage/emulated/0/Android/data/com.bithack.principia/files/ (see Accessing Android Data Directory)
c: cURL cookie file. NOTE: Do not share this with anyone, as this will allow them to grab your principia-web login token!
data.bin: Contains miscellaneous game data such as package completion and highscore tracking.
fl.cache: Cached data for the main menu featured levels list.
models.cache: Cache files for fonts and models respectively to make the game load faster. They will be regenerated on next startup if deleted.
settings.ini: INI text file with game settings.
cache/: Level cache. Temporary Lua files for editing in an external editor get saved here.
lvl/: The place where levels are saved.
pkg/: The place where packages are saved.
sav/: Saved games that can be continued from the main menu.
pkg/, they are further split into "namespaces".
db: Community site levels gets downloaded locally to this namespace before they are played.
local: This is where you find your locally saved levels!
main: Primarily for built-in levels (e.g. the built-in puzzle package), is usually always empty in the user data folder.