clarification

src/game.rs

@@ -3,8 +3,9 @@ use std::error::Error;
 use loe::TransformMode;
 use std::str::FromStr;
 
-/// in very early versions of Bitsy, room tiles were defined as single characters
-/// so, only 36 tiles total. later versions are comma-separated
+/// in very early versions of Bitsy, room tiles were defined as single alphanumeric characters -
+/// so there was a maximum of 36 unique tiles. later versions are comma-separated.
+/// RoomFormat is implemented here so we can save in the original format.
 #[derive(Debug, Eq, PartialEq, Copy, Clone)]
 pub enum RoomFormat {Contiguous, CommaSeparated}