Game tracks all information regarding your game progress.
Every time you hit New Game, a new game session is created, and previous game session ends (if was started before). In this case game will warn you and will ask if you want to start over.
Every game session saves data about which levels you completed, how many Gems and Coins you collected in each level, the Grade you received in every level, and level play time. Every session has information about the overall score (as a sum of scores of every successfully completed level), as well as a number of Bonus Levels played overall in this session.
You can see all game sessions in the Scores section on the main game screen, and you can click (or press action button on your gamepad) to open a window displaying a list of levels you played in this perticular game session. Every session has status – In Progress or Completed. Not more than one In Progress game session can be in the list at any time.
Only successfully completed levels add up to your session score. Bonus Levels always add up to your session score regardless of their completion result. When the game is paused, in-level time counter pauses too.