Crystal Engine. The engine and the game's content were developed in parallel, leading to scheduling and workload difficulties. Anniversary used the same engine as Legend. Underworld used a new engine built specifically for the game, although its basic codebase was shared with Legend. In Underworld, Lara's movements were animated using full motion capture, with Olympic gymnast Heidi Moneymaker providing the character's animations. For the 2013 reboot, a new engine called Foundation was created for the game. Motion capture was again used for this title. An updated version of the Foundation engine was used again for Rise of the Tomb Raider. For both games in the new reboot, Lara's hair movements were made more realistic using a technology called TressFX in Tomb Raider and PureHair in Rise of the Tomb Raider. The Foundation engine remained in use for the third entry in the reboot series, Shadow of the Tomb Raider, and featured new graphical enhancements from developer Eidos-Montréal. Cultural impact Both the character of Lara Croft and the concepts behind the Tomb Raider franchise have evolved thematically and in popularity since the first game's release in 1996. The success of the game series led to several commercial tie-ins that further catapulted to cultural icon status, including feature spin-off games, feature films, and comics. Reception Upon release, Tomb Raider became an unexpected success, reaching the top of sales charts and remaining for a time. It went on to sell over 7 million units worldwide. Tomb Raider II was a greater commercial success, with debut sales higher than the first game and total worldwide sales of 8 million units. Despite varying critical receptions, series sales continued to be strong until the release of Chronicles, which sold 1.5 million units. While The Angel of Darkness met with initial strong sales, it failed to meet expectations. Since the release of Legend, the series has picked up in sales and popularity. The 2013 reboot sold 11 million units, becoming the most commercially successful Tomb Raider title to date. As of 2021, the series has sold over 85 million units worldwide. In addition to the games' success, the 2001 film adaptation grossed $275 million, making it the highest-grossing video game adaptation until being overtaken in 2010 by Prince of Persia: The Sands of Time. Additionally, the first Tomb Raider comic book issue was the best-selling comic book of 1999 and the 2001 film adaptation had the biggest