I'm not sure specifically as it could be a rather unique or niche visual novel. It might involve a character with a keyboard for a head in some sort of strange or interesting story world. Maybe it's about a world where technology and the human form are merged in a very odd way.
Without having read or known more about this particular visual novel, it's just speculation. However, perhaps there's a scientist character who created the keyboard - head character in the story. There could also be a love interest for the keyboard - head character, someone who sees past their strange appearance and falls in love with their true self, which would add a romantic sub - plot to the story.
The duration of the Chaos Head visual novel is not fixed. It can take anywhere between 15 and 25 hours for a thorough playthrough, factoring in different playstyles and the extent of interaction with the story elements.
There may be some 'head pat visual novel' titles out there that are popular among fans of the genre. However, it's not as mainstream as some other types of visual novels. It could be that in some Japanese - made visual novels, which are known for their diverse themes, there might be some that feature head patting prominently. But without extensive research, it's hard to name specific popular titles.
A 'head pat visual novel' is likely a type of visual novel that may involve the action of head patting. It could be a story - based game where characters interact and head patting might be a form of affection or interaction within the narrative.
The anime of Chaos Head is a condensed version of the visual novel. The visual novel usually has more in - depth storylines and character developments as it can afford to be more detailed. In the anime, some plotlines might be simplified or cut for the sake of fitting into a limited number of episodes.