Starting from version 1.10.0 you can gain experience (stars) and achieve different levels in the game when the star is filled up.
Currently Level 250 is the highest level you can reach.
With every odd level achievement you receive coins and with every even level achievement you receive a free pack that can be downloaded from the Free section in the Puzzle Shop (scroll down the bar with the packs).
You can check how many stars you need for reaching the new level.
Please tap the star at the top.