Hearts: You need to have at least one heart to play puzzles. You can keep up to 5 hearts in the heart booth, and you lose a heart when you fail to complete a stage. When you have 4 or fewer hearts, you will get a free heart every 30 minutes until your heart booth is fully restored.
Canned Sardines: This is the in-game currency. You can use them to add extra moves/time or buy boosters and hearts when playing puzzles. You can get free Canned Sardines when you complete a stage or as a login bonus.
Canned Sardines: Available for purchase from the Fortune Store.
Hearts: Buy them using Canned Sardines.
Sending/requesting hearts: Click <HERE> for more details.