Crush pornography features objects being crushed by an actress or actor, who generally plays an overtly dominant role. His most famous model was Bettie Page, who became the first celebrity of bondage film and photography. Boots are seen as the perhaps most fetishistic of all footwear and boots may be the most popular fetish clothing attire. The industry generally refers to such films as adult horny milfs films, which is part of adult entertainment. The current public acceptance hentai sex of celebrities with sex tapes is speculated by Joe Levy, executive editor of Rolling Stone, gay bear porn to be due to the easy availability of pornography, as well as couples more commonly making their own tapes due to the prevalence of video cameras. In S/M, the Sadist is usually the Top and the Masochist the Bottom, but these roles are frequently more complicated or jumbled . This makes varying degrees of stimulation an integral part of oral sex for many men. Examples of mentally oriented practices are education games, during which the dominant requires certain forms of behavior from the submissive. Mutual masturbation, mutual manual stimulation of the genitals between partners, can be a substitute for sexual penetration. Snowballing or snowdropping is the human sexual practice in which one person takes someone else semen into his or her mouth and then passes it to the mouth of the other, usually through kissing. Spanking can be administered in a number of spanking positions. Following the introduction of the Motion Picture Association of America film rating system, independent animation producers attempted to establish an alternative to mainstream animation. A related term used in the genre is the term cougar, which implies an older woman as predator. Real school shots or videos which are sexualized may violate privacy laws in some countries. Bondage pornography specializes in the depiction of sexual bondage or BDSM activities as photographs, stories, movies, or drawings. Standing up, a chair, the corner of an item of furniture, or even a washing machine can be used to stimulate the clitoris through the labia and clothing.