RPS - Linear, Sandbox, or Something Else?

It's hard to classify Rock, Paper, Scissors as linear or sandbox. It's an incredibly short and simple game, and hardly fits any model that would categorize other games. The structure of the game does give it a clear set of directions and a specific goal, and playing it is very straightforward. There is little room for any variation or experimentation, so if it comes down to linear versus non-leaner/sandbox, RPS would have to be categorized as linear. I think it makes more sense to group short, simple games that really lack a linear or sandbox structure into their own group though. Games like rps, tic-tac-toe, odds or evens, etc. don't fit into either group and would be more suited to their own classification.