Calvin and Hobbs know about the magic circle and are great game designers, they design the rules while playing the game.
Wikipedia on Calvinball: “The only consistent rule states that Calvinball may never be played with the same rules twice. Scoring is also arbitrary, with Hobbes at times reporting scores of “Q to 12” and “oogy to boogy”
What I recognise… is their desire to stay inside the magic circle in playing this game, but meanwhile trying to push the boundaries of the magic circle, when will it “snap?”
(check my interpretation on the magic circle if this sounds weird)