My suggestion for the system would be something like this, feel free to chime in and add something in:
* = crude language, this would be things like the f -bomb and bastard and other major swear words, it would have mild sexual situations, where it's more suggestion than anything substantial. Like Teen level
** = this would have mild/medium graphic violence, small or not very detailed sexual content and crude words.
*** = this would have sexual situations, like adult romance novel level. it would have medium/high graphic violence and or course crude language.
**** = here's the biggie this is erotic level and slasher movie level. All erotic content can go here, and all levels of violence. there would be disturbing themes and such. it would be enter at your own risk.
***** = I don't know if there would be any of this content of here but say for instance there was content with things like bondage, bestiality, incest, and such it would go here. All the stuff that society has issues with. that sort of stuff.
Feel free to edit and add to this list. I just made a rough idea. It's only an idea.
