diff --git a/.tool-versions b/.tool-versions
new file mode 100644
index 0000000..342a21f
--- /dev/null
+++ b/.tool-versions
@@ -0,0 +1,2 @@
+dojo 1.0.0-alpha.5
+scarb 2.7.0
diff --git a/src/models/evolution.cairo b/src/models/evolution.cairo
index 8ac091f..f9fc761 100644
--- a/src/models/evolution.cairo
+++ b/src/models/evolution.cairo
@@ -14,11 +14,17 @@ struct Evolution {
 }
 
 mod rules {
-    // Minimum rule to envolve
-    const ENVOLVED_BEAST_ID: u32 = 2;
+    /// Minimum rules for beast evolution
+
+    /// The ID assigned to the evolved beast form
+    const EVOLVED_BEAST_ID: u32 = 2;
+    /// Minimum level required before evolution is possible
     const LEVEL_REQUIREMENT: u32 = 10;
+    /// Minimum number of battles required before evolution
     const REQUIRED_BATTLES: u32 = 5;
+    /// Item ID required for evolution (special evolution stone)
     const REQUIRED_ITEM: u32 = 1001;
+
 }
 
 #[generate_trait]
@@ -29,16 +35,17 @@ impl EvolutionImpl of EvolutionTrait {
             Option::None => true,
        };
 
-       is_valid_item && self.level_requirement >= rules::LEVEL_REQUIREMENT && self.required_battles >= rules::REQUIRED_BATTLES
+        is_valid_item &&
+            self.level_requirement > rules::LEVEL_REQUIREMENT &&
+            self.required_battles > rules::REQUIRED_BATTLES
     }
 
-    fn envolve(ref self: Evolution) -> Result<u32, felt252>  {
+    fn evolve(self: Evolution) -> Result<u32, felt252>  {
+        assert(self.base_beast_id != 0, 'Invalid base beast');
+
         match self.can_evolve() {
-            true => {
-                self.evolved_beast_id = rules::ENVOLVED_BEAST_ID;
-                Result::Ok(self.evolved_beast_id)
-            },
-            false => Result::Err('Invalid Evolution'),
+            true => Result::Ok(rules::EVOLVED_BEAST_ID),
+            false => Result::Err('Evolution requirements not met'),
         }
     }
 }
\ No newline at end of file