Fun game, light strategy, but needs more birds. You can advance to higher levels, but they are no more challenging than the lower levels, because the number and types of birds don’t change. Compared to similar games I’ve tried this is the best, though, as the 5-second ads really are only 5 seconds long and are typically only one per level of play. Recent change of opinion: this game used to have short ads like 5-seconds-and-done with a Return to Game option if the ad ran long. That is no longer true. It now has the same frequent and interminable ads that every other game has.