's 2015 DMC Festival. On June 30, 2015, the group released music video previews of three then-forthcoming singles "
Party", "
Lion Heart" and "
You Think", serving as a promotional tool for their first
Korean language studio album as an eight-member group. Details on album, including its title, release date, cover artwork and track list, were announced on August 12, 2015. The group's label,
SM Entertainment, revealed that the record would be released in the span of two days. The first six songs—including the single "Lion Heart"—would be made available on August 18, while the remaining tracks—including the single "You Think"—would be distributed on the following day;
Billboard described the release strategy as "atypical." An alternative edition of the album featuring a different artwork was additionally released on August 26, 2015, under the title
You Think. Following the release of the record, Girls' Generation appeared on several South Korean music programs, including
KBS's
Music Bank,
MBC's
Show! Music Core, and
SBS'
Inkigayo, in order to promote the record, with them performing "Lion Heart" and "You Think". Throughout August 18–25, the group also participated and interacted with viewers through a series of mobile video live stream on
Naver's mobile application "V". Subsequently, the group additionally embarked on a concert tour titled
Girls' Generation's Phantasia, which kicked off on November 21, 2015, at the
Olympic Gymnastics Arena in
Seoul, and continued in visiting
Japan,
Thailand,
Indonesia and
Taiwan. "Party" was made available as the
lead single from
Lion Heart for
digital purchase by SM on July 7, 2015. The physical
CD single was made available for purchase on July 8, 2015. An accompanying music video for the recording was released in conjunction with the release of the single. Commercially, "Party" debuted atop the
Gaon Digital Chart on the chart issue dated July 11, 2015, selling 256,390 digital units within its first week of availability, bringing total sales to over 843,843 digital units in South Korea as of December 2015, thus becoming the 58th best-selling single of 2015. "Party" additionally peaked at number ten on the
Japan Hot 100 and number four on the
Billboard World Digital Songs. The title track was serviced as the album's second single, and its music video premiered on August 18, 2015. while "You Think" impacted KBS radio on August 23. Both songs charted on the Gaon Digital Chart, peaking at numbers four and 30, respectively. == Critical reception ==