diff --git a/src/cdl_parser/constants.py b/src/cdl_parser/constants.py
index 6d66c1b..415eaec 100644
--- a/src/cdl_parser/constants.py
+++ b/src/cdl_parser/constants.py
@@ -139,15 +139,29 @@
 
 FEATURE_NAMES: set[str] = {
     # Growth features
-    "phantom", "sector", "zoning", "skeletal", "dendritic",
+    "phantom",
+    "sector",
+    "zoning",
+    "skeletal",
+    "dendritic",
     # Surface features
-    "striation", "trigon", "etch_pit", "growth_hillock",
+    "striation",
+    "trigon",
+    "etch_pit",
+    "growth_hillock",
     # Inclusion features
-    "inclusion", "needle", "silk", "fluid", "bubble",
+    "inclusion",
+    "needle",
+    "silk",
+    "fluid",
+    "bubble",
     # Color features
-    "colour", "colour_zone", "pleochroism",
+    "colour",
+    "colour_zone",
+    "pleochroism",
     # Other
-    "lamellar", "banding",
+    "lamellar",
+    "banding",
 }
 
 # =============================================================================
@@ -155,6 +169,12 @@
 # =============================================================================
 
 PHENOMENON_TYPES: set[str] = {
-    "asterism", "chatoyancy", "adularescence", "labradorescence",
-    "play_of_color", "colour_change", "aventurescence", "iridescence",
+    "asterism",
+    "chatoyancy",
+    "adularescence",
+    "labradorescence",
+    "play_of_color",
+    "colour_change",
+    "aventurescence",
+    "iridescence",
 }
diff --git a/src/cdl_parser/models.py b/src/cdl_parser/models.py
index 05533e2..c0fc221 100644
--- a/src/cdl_parser/models.py
+++ b/src/cdl_parser/models.py
@@ -246,20 +246,18 @@ def _form_node_to_dict(node: FormNode) -> dict[str, Any]:
             "scale": node.scale,
             "name": node.name,
             "label": node.label,
-            "features": [
-                {"name": feat.name, "values": feat.values}
-                for feat in node.features
-            ] if node.features else None,
+            "features": [{"name": feat.name, "values": feat.values} for feat in node.features]
+            if node.features
+            else None,
         }
     elif isinstance(node, FormGroup):
         return {
             "type": "group",
             "forms": [_form_node_to_dict(f) for f in node.forms],
             "label": node.label,
-            "features": [
-                {"name": feat.name, "values": feat.values}
-                for feat in node.features
-            ] if node.features else None,
+            "features": [{"name": feat.name, "values": feat.values} for feat in node.features]
+            if node.features
+            else None,
         }
     return {}
 
@@ -346,10 +344,9 @@ def to_dict(self) -> dict[str, Any]:
                     "scale": f.scale,
                     "name": f.name,
                     "label": f.label,
-                    "features": [
-                        {"name": feat.name, "values": feat.values}
-                        for feat in f.features
-                    ] if f.features else None,
+                    "features": [{"name": feat.name, "values": feat.values} for feat in f.features]
+                    if f.features
+                    else None,
                 }
                 for f in self.flat_forms()
             ],
@@ -373,7 +370,9 @@ def to_dict(self) -> dict[str, Any]:
             "definitions": [
                 {"name": d.name, "body": [_form_node_to_dict(f) for f in d.body]}
                 for d in self.definitions
-            ] if self.definitions else None,
+            ]
+            if self.definitions
+            else None,
         }
 
 
@@ -386,10 +385,15 @@ def _flatten_node(
             merged = list(parent_features)
             if node.features:
                 merged.extend(node.features)
-            return [CrystalForm(
-                miller=node.miller, scale=node.scale,
-                name=node.name, features=merged, label=node.label,
-            )]
+            return [
+                CrystalForm(
+                    miller=node.miller,
+                    scale=node.scale,
+                    name=node.name,
+                    features=merged,
+                    label=node.label,
+                )
+            ]
         return [node]
     elif isinstance(node, FormGroup):
         combined_features = list(parent_features) if parent_features else []
diff --git a/src/cdl_parser/parser.py b/src/cdl_parser/parser.py
index c7c935c..61a8672 100644
--- a/src/cdl_parser/parser.py
+++ b/src/cdl_parser/parser.py
@@ -70,6 +70,7 @@ def strip_comments(text: str) -> tuple[str, list[str]]:
 
     return text, doc_comments
 
+
 # =============================================================================
 # Token Types
 # =============================================================================
@@ -433,7 +434,10 @@ def parse(self) -> CrystalDescription:
         phenomenon = None
         if self._current().type == TokenType.PIPE:
             self._advance()  # consume |
-        if self._current().type == TokenType.IDENTIFIER and self._current().value.lower() == "phenomenon":
+        if (
+            self._current().type == TokenType.IDENTIFIER
+            and self._current().value.lower() == "phenomenon"
+        ):
             phenomenon = self._parse_phenomenon()
 
         return CrystalDescription(
@@ -792,7 +796,11 @@ def _parse_phenomenon(self) -> PhenomenonSpec:
                 else:
                     # Bare identifier value
                     params[key] = True
-            elif self._current().type in (TokenType.INTEGER, TokenType.FLOAT, TokenType.POINT_GROUP):
+            elif self._current().type in (
+                TokenType.INTEGER,
+                TokenType.FLOAT,
+                TokenType.POINT_GROUP,
+            ):
                 val = self._parse_feature_value()
                 params["value"] = val
 
diff --git a/tests/test_parser.py b/tests/test_parser.py
index 39924ca..b380d2d 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -572,11 +572,7 @@ def test_multiple_doc_comments(self):
 
     def test_mixed_comments(self):
         """Mix of line, block, and doc comments."""
-        cdl = (
-            "#! Mineral: Quartz\n"
-            "# A line comment\n"
-            "/* block */ trigonal[-3m]:{10-10} # inline"
-        )
+        cdl = "#! Mineral: Quartz\n# A line comment\n/* block */ trigonal[-3m]:{10-10} # inline"
         desc = parse_cdl(cdl)
         assert desc.system == "trigonal"
         assert desc.doc_comments == ["Mineral: Quartz"]
@@ -1101,6 +1097,7 @@ class TestVersion:
     def test_version_1_3(self):
         """Version is 1.3.0."""
         import cdl_parser
+
         assert cdl_parser.__version__ == "1.3.0"