replace tile ID with string

src/tile.rs

@@ -3,7 +3,7 @@ use crate::image::animation_frames_from_string;
 
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct Tile {
-    pub id: u64,
+    pub id: String,
     pub name: Option<String>,
     pub wall: Option<bool>, // this is "optional" in that a tile can have `WAL true|false` or neither
     pub animation_frames: Vec<Image>,
@@ -40,7 +40,7 @@ impl From<String> for Tile {
     fn from(string: String) -> Tile {
         let mut lines: Vec<&str> = string.lines().collect();
 
-        let id = from_base36(&lines[0].replace("TIL ", ""));
+        let id = lines[0].replace("TIL ", "");
 
         let mut wall = None;
         let mut name = None;
@@ -80,7 +80,7 @@ impl ToString for Tile {
     fn to_string(&self) -> String {
         format!(
             "TIL {}\n{}{}{}{}",
-            self.id.to_base36(),
+            self.id,
             self.animation_frames.to_string(),
             self.name_line(),
             self.wall_line(),
@@ -100,7 +100,7 @@ mod test {
         let output = Tile::from(include_str!("test-resources/tile").to_string());
 
         let expected = Tile {
-            id: 35,
+            id: "z".to_string(),
             name: Some("concrete 1".to_string()),
             wall: Some(true),
             animation_frames: vec![Image {
@@ -115,7 +115,7 @@ mod test {
     #[test]
     fn test_tile_to_string() {
         let output = Tile {
-            id: 262,
+            id: "7a".to_string(),
             name: Some("chequers".to_string()),
             wall: None,
             animation_frames: vec![