The Fluffian Kingdom has had a long history. There were ten kingdoms: The Red kingdom, The Amber Kingdom, The Chartreuse Kingdom, The Forest Kingdom, The Cyan Kingdom, The Blue Kingdom, The Indigo Kingdom, The Rose Kingdom, The Ice Kingdom and the Unknown Kingdom. The Amber kingdom died because of an economic crisis. The Charteruse Kingdom died of Famine. The Forest kingdom was converted by Blue kingdom missionaries. Both the Cyan and Indigo kingdom died of radiation poisoning from the lesser mushroom wars. Rose kingdom died of plague. Ice kingdom died of because of a sudden rise in temperature. Nobody knows what happened to the Unknown kingdom. All of its inhabitants and infrastructure disappeared in less than a day, and one hundred years later there was a huge explosion in the area. There is an unusually high amount of radiation, and the temperatures there are now frigid. It could be the cause of the demise of the Cyan, Indigo and Ice kingdom. also, due to these conditions, neither fluffy nor machine has ventured in there successfully. There was a war fought between the Blue kingdom and the Red kingdom, and the Red kingdom won.
And that's why fluffies have red semicircles.