following some clippy recommendations

src/game.rs

@@ -6,7 +6,7 @@ use std::str::FromStr;
 use std::collections::HashMap;
 use std::borrow::BorrowMut;
 use std::fmt;
-use std::fmt::Display;
+use std::fmt::{Display, Formatter};
 
 /// 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.
@@ -25,12 +25,14 @@ impl RoomFormat {
             _   => Err(InvalidRoomFormat),
         }
     }
+}
 
-    fn to_string(&self) -> String {
-        match &self {
+impl Display for RoomFormat {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", match &self {
             RoomFormat::Contiguous     => "0",
             RoomFormat::CommaSeparated => "1",
-        }.to_string()
+        })
     }
 }
 
@@ -826,22 +828,17 @@ impl Game {
     }
 
     fn font_line(&self) -> String {
-        if self.font == Font::AsciiSmall {
-            "".to_string()
-        } else {
-            if self.font == Font::Custom {
-                format!("\n\nDEFAULT_FONT {}", self.custom_font.as_ref().unwrap())
-            } else {
-                format!("\n\nDEFAULT_FONT {}", self.font.to_string().unwrap())
-            }
+        match self.font {
+            Font::AsciiSmall => "".to_string(),
+            Font::Custom     => format!("\n\nDEFAULT_FONT {}", self.custom_font.as_ref().unwrap()),
+            _                => format!("\n\nDEFAULT_FONT {}", self.font.to_string().unwrap()),
         }
     }
 
     fn text_direction_line(&self) -> &str {
-        if self.text_direction == TextDirection::RightToLeft {
-            "\n\nTEXT_DIRECTION RTL"
-        } else {
-            ""
+        match self.text_direction {
+            TextDirection::RightToLeft => "\n\nTEXT_DIRECTION RTL",
+            _ => "",
         }
     }