Can be fun for a while, but as you play more strategy (to combine boosters for example) , you start to realize the game is rigged to encourage purchases of boosters. It literally cheats you out of your skillful efforts. If you can accept this, just play without spending a dime and be ready to play many levels over and over until it gives it to you. The internal cheating has ruined the game for me so just uninstalling and moving on.