Every day, you can play free daily levels called "Daily Puzzles" that allow you to earn rewards. These are normal grids, with a list of defined words to be found within a given time.
If you have found all the words on the list before the time runs out, the Daily Puzzle's gift gauge will increase.
If the time is up and you haven't finished, you can continue the grid by buying an additional 30 seconds with coins (in the form of an Hourglass, which you can get for free by watching a video ad or by buying a lot in the dedicated shop), or leave the puzzle. Be careful, a Daily Puzzle that you leave is lost and cannot be played again.
You can buy an Infinite Hourglass in order to be able to play Daily Puzzles without any time constraint. This Infinite Hourglass is a permanent purchase.