Immersion is a state of being so focused on a specific problem or experience that there are no distractions. Blocking out distractions makes it possible to stimulate the senses to tap imagination, provide new experiences, and increase a person's knowledge or awareness. Immersion can be achieved in part by the illusion of reality, whether that reality is familiar or some new, plausible but unfamiliar place (inside a protein molecule, flying over Mars) and in part by merely engaging the senses, delighting the imagination and holding the user's attention much as theater does.