"Sex scene" refers to all sexual acts, including but not limited to masturbation, any and all sexually intimate scenes which may involve orgasms and the lead up to orgasms, and any and all forms of sexual penetration.
Heat Level 0
There may be a kiss or two, but there are no sex scenes on or off the page.
Heat Level 1
Kissing is involved. At least one sex scene may be mentioned, but sex scene(s) are off-page.
Heat Level 2
Kissing and make-out sessions. At least one sex scene may be on-page, but sex scene(s) are either closed door or not explicitly described.
Heat Level 3
Kissing and make-out sessions. At least one sex scene(s) is explicitly described on-page.
Heat Level 4
Kissing and make-out sessions. There are multiple explicitly described sex scenes present.