Oppai Slider 2
Oppai Slider 2 (おっぱいスライダー２) is a Japanese 3D sex simulator developed by Illusion Soft. It features three girls of different temperaments and willingness who the player tries to make aroused and ready for sex through the use of various objects and manipulation of erogenous zones. The name, containing a Japanese slang term for breasts, is a reference to the game's numerous options for customizing the size and appearance of female characters' breasts, nipples, and various other options like clothing transparency level and hair color through the use of the slider mechanic that makes extensive use of the mouse's scroll wheel. Much of the interaction in the game relies on the scroll wheel as well.
Read article on Wikipedia