Men may also rub or massage the glans, the rim of the glans, and the frenular delta. Interactive pornography, available in CD-ROM and DVD format, allows the viewer to select the particular acts performed at any one time, sometimes with the camera providing a first person view. The term bondage describes the practice of Physical restraining. Double Stuffed , Double Vaginal , or Double Anal pornography involves the penetration of one orifice by two penises or other objects. A bisexual threesome may involve a man having sex with a man and a woman, the woman having sex with a man and a woman, or all three having sex with each other. Preggo pornography features pregnant performers momsex and hentai videos may include erotic lactation as a fetish. It is also known colloquially as gushing or squirting, gay twinks although these are considered to be different phenomena in some research publications. Compensating elements of the total dominance and submission are care and devotion complementing one another, thus facilitating stable relationships. As a form of non-penetrative sex, it can be done for its own enjoyment or as foreplay. Group sex pornography features at least two men and two women , usually more, who all perform sex acts on each other. Double penetration of the vagina, anus and mouth, can involve: Simultaneous penetration of the anus by two penises or other objects. Solo performances in gay pornography have been described in 1985 as either or both active and/or passive , whereas female solo performances are said to be exclusively passive . Patricia Hill Collins, an African-American writer, theorizes that this is derived from a stereotype that those of black descent are promiscuous, and their buttocks are objectified by porn as a result. It is typically animated pornography, as the legal age to be featured in a pornographic film in Japan is 18. Starting with erotic stories and woodblock prints from before the 20th century, Japanese pornography evolved into distinct subcategories with the media that in addition of pornographic videos and magazines featuring live actors, there is exist categories of pornographic manga , pornographic computer games , and pornographic anime .