While I agree with the idea that there is merit to a proper and well designed national id for official uses, I disagree with the idea of attaching it to R18 content. The way I see it, trying to do so inevitably intrudes on people's privacy in some way (content providers might collect that ID to check against government records, leading to the risk that they improperly store it, for example, or the government might be tempted to police the activities of adults to an unreasonable level, or at least creates the infrastructure to do so if a more restrictive government came into power). Further, it will not and fundamentally cannot stop kids from accessing things deemed inappropriate for them, because kids are curious, and the things one wants to restrict in this way are generally information, which is trivially easy for them to copy and distribute among themselves. I think we need better education, both to children/teenagers (depending on the subject) about those topics we as a society seem averse to the idea of them knowing about, but which they will inevitably learn of anyway (things like sex-ed, or how to deal with drug addiction or its presence among people they might know (and not just in the counterproductive way that things like DARE used to do)), and to parents about how to deal with children becoming curious about or trying to access restricted topics. Beyond that, I think we should generally leave it to parents to parent their children. While it might not be ideal if some kid gets access to a video game rated for adults, it also isnt physically dangerous to them in the way that something like alcohol is, so treating it the same way is overkill at best.