Their team had spent months on a fantasy themed Facebook game when Supercell changed strategies. Leppinen and Louhento wanted to make a strategy game that would use a touch screen so playing would be as simple and pleasant as possible. The development of Clash of Clans took six months, and the game was released on 2 August 2012. In three months, it became the most profitable app in the US. According to App Annie, in the years 2013 and 2014 Clash of Clans was the most profitable mobile game in the world. The eponymous battle between the clans was added to the game as late as 2014. In summer 2013, Supercell began a marketing collaboration with the Japanese video game company GungHo: the companies cross-marketed each other's games in their own markets. As a result, Clash of Clans became one of the most downloaded apps in Japan. GungHo's chairman of the board Taizo Son flew to Finland to thank Paananen and later introduced him to his brother Masayoshi Son, the CEO of the SoftBank Corporation. Soon, they proposed a corporate acquisition which indeed happened on 7 October 2013. SoftBank and GungHo bought 51% of Supercell's shares for 1.1 billion euros which is the largest price for a Finnish private company in history. In six months, Supercell's value had tripled, since in spring 2013 the company had sold 16.7% of its shares for 100 million euros. Development of games after Clash of Clans Both Clash of Clans and Hay Day were released in summer 2012, and Supercell did not release a new game in almost two years. The design of the third game Boom Beach started in the autumn of 2012, and it was released in 2014. The new strategy game was released to the test market at the end of 2013, after which it went through large changes. The game was very successful in the US right after its release in March, but it did not stay at the top of the download charts for very long. However, it rose to the top 30 of the most downloaded iPhone apps after Supercell started an expensive marketing campaign in December 2014. In 2015, the game surpassed Hay Day in the charts. In March 2016, Supercell released its fourth supported game, Clash Royale, which uses similar characters from Clash of Clans. Between the releases of Boom Beach and Clash Royale, Supercell had