The late-1980s saw the development of a new muscle-based model by Waters, the development of an abstract muscle action model by Magnenat-Thalmann and colleagues, and approaches to automatic speech synchronization by Lewis and Hill. The 1990s have seen increasing activity in the development of facial animation techniques and the use of computer facial animation as a key storytelling component as illustrated in animated films such as "Toy Story" (1995), "Antz" (1998), "Shrek", and "Monsters, Inc." (both 2001), and computer games such as "Sims". "Casper" (1995), a milestone in this decade, was the first movie in which a lead actor was produced exclusively using digital facial animation.