Seasons introduced 25 Christmas-themed levels, one for each day leading to the holiday, similar to an Advent calendar. All versions include the previously-exclusive Halloween levels and are offered as separate, stand-alone paid applications, with the exception of the free, ad-supported Android version; Angry Birds Halloween users on iOS received the Seasons levels as a free upgrade. The Halloween version was given the episode title “Trick or Treat”, while the Christmas episode was entitled “Season’s Greedings”. In February 2011, Rovio released a new Valentine’s Day update to Angry Birds Seasons, entitled “Hogs and Kisses”, complete with new themed levels and graphics, as well as the option to send Angry Birds-themed Valentine’s Day messages through Facebook. In March 2011, Rovio released a new St. Patrick’s Day update, entitled “Go Green, Get Lucky”,followed by an Easter update, entitled “Easter Eggs”, in April 2011 and a summer update, “Summer Pignic”, in June 2011.In September 2011, “Mooncake Festival” was released in conjunction with the Chinese Mid-Autumn Festival.In October 2011, “Ham’O’Ween” was released and introduced a new orange bird, known as the globe bird