Trying to figure this one out for the longest. In the film a young female teenage is drawn in by a satanic trio of male teenagers who are seemingly demons, because she likes one of them. She also has a little brother who ends up watching the satanic ritual they initiate in an abandoned cave which culminates in them having sex with her. One of the other details in the movie I remember is a character who invented a super lawnmower and likes the girl. He ends be murdered by the demonic trio being killed by his own lawnmower. That’s all I can remember though!