add separate sort order field to levels, so they can be reordered without changing the id and invalidating solutions

src/level.rs

@@ -3,6 +3,7 @@ use serde::Deserialize;
 #[derive(Debug, Clone, Deserialize)]
 pub struct Level {
 	id: String,
+	sort_order: i32,
 	name: String,
 	description: String,
 	init_board: Option<String>,
@@ -15,6 +16,10 @@ impl Level {
 		&self.id
 	}
 
+	pub fn sort_order(&self) -> i32 {
+		self.sort_order
+	}
+
 	pub fn name(&self) -> &str {
 		&self.name
 	}

src/main.rs

@@ -236,7 +236,7 @@ fn get_levels() -> Vec<Level> {
 			levels.push(level);
 		}
 	}
-	levels.sort_by(|a, b| a.id().cmp(b.id()));
+	levels.sort_by(|a, b| a.sort_order().cmp(&b.sort_order()));
 	levels
 }