diff --git a/phase1-json-schema.md b/phase1-json-schema.md
index 980e385..87364bf 100644
--- a/phase1-json-schema.md
+++ b/phase1-json-schema.md
@@ -10,6 +10,8 @@ PHY (物理配置) → IDX (キー識別) → ELC (電気配線) + MAP (キー
 
 ## 1. PHYレイヤー JSON Schema
 
+座標・回転・サイズの意味は `PHYレイヤー.md` を正とする。
+
 ### 基本構造
 
 ```json
@@ -19,7 +21,7 @@ PHY (物理配置) → IDX (キー識別) → ELC (電気配線) + MAP (キー
   "title": "PHY Layer - Physical Key Layout",
   "description": "Physical positioning and sizing of keys",
   "type": "object",
-  "required": ["version", "metadata", "profiles", "elements"],
+  "required": ["version", "metadata", "profiles", "root"],
   "properties": {
     "version": {
       "type": "string",
@@ -61,7 +63,7 @@ PHY (物理配置) → IDX (キー識別) → ELC (電気配線) + MAP (キー
         "$ref": "#/$defs/profile"
       }
     },
-    "elements": {
+    "root": {
       "type": "array",
       "items": {
         "oneOf": [
@@ -72,6 +74,16 @@ PHY (物理配置) → IDX (キー識別) → ELC (電気配線) + MAP (キー
     }
   },
   "$defs": {
+    "transform": {
+      "type": "object",
+      "description": "Placement relative to the parent: rotate by rotation around the local origin, then translate by (x, y)",
+      "required": ["x", "y", "rotation"],
+      "properties": {
+        "x": { "type": "number" },
+        "y": { "type": "number" },
+        "rotation": { "type": "number", "description": "Degrees" }
+      }
+    },
     "profile": {
       "type": "object",
       "required": ["id", "name", "unitSize"],
@@ -98,7 +110,7 @@ PHY (物理配置) → IDX (キー識別) → ELC (電気配線) + MAP (キー
     },
     "key": {
       "type": "object",
-      "required": ["type", "id", "profile", "position", "size"],
+      "required": ["type", "id", "profile", "transform", "size"],
       "properties": {
         "type": {
           "type": "string",
@@ -112,28 +124,14 @@ PHY (物理配置) → IDX (キー識別) → ELC (電気配線) + MAP (キー
           "type": "string",
           "description": "Reference to profile ID"
         },
-        "position": {
-          "type": "object",
-          "required": ["x", "y"],
-          "properties": {
-            "x": { "type": "number" },
-            "y": { "type": "number" },
-            "rotation": { "type": "number" },
-            "rotationOrigin": {
-              "type": "object",
-              "properties": {
-                "x": { "type": "number" },
-                "y": { "type": "number" }
-              }
-            }
-          }
-        },
+        "transform": { "$ref": "#/$defs/transform" },
         "size": {
           "type": "object",
-          "required": ["width", "height"],
+          "description": "Local size. Not affected by the parent transform",
+          "required": ["w", "h"],
           "properties": {
-            "width": { "type": "number", "minimum": 0 },
-            "height": { "type": "number", "minimum": 0 }
+            "w": { "type": "number", "minimum": 0 },
+            "h": { "type": "number", "minimum": 0 }
           }
         },
         "metadata": {
@@ -146,7 +144,6 @@ PHY (物理配置) → IDX (キー識別) → ELC (電気配線) + MAP (キー
               "type": "object",
               "description": "Original KLE fields for round-trip compatibility",
               "properties": {
-                "originalIndex": { "type": "integer" },
                 "labels": { "type": "array", "items": { "type": "string" } },
                 "textSizes": { "type": "array", "items": { "type": "number" } },
                 "decalData": { "type": "object" }
@@ -158,7 +155,7 @@ PHY (物理配置) → IDX (キー識別) → ELC (電気配線) + MAP (キー
     },
     "cluster": {
       "type": "object",
-      "required": ["type", "id", "name", "elements"],
+      "required": ["type", "id", "name", "transform", "children"],
       "properties": {
         "type": {
           "type": "string",
@@ -166,22 +163,8 @@ PHY (物理配置) → IDX (キー識別) → ELC (電気配線) + MAP (キー
         },
         "id": { "type": "string" },
         "name": { "type": "string" },
-        "position": {
-          "type": "object",
-          "properties": {
-            "x": { "type": "number" },
-            "y": { "type": "number" },
-            "rotation": { "type": "number" },
-            "rotationOrigin": {
-              "type": "object",
-              "properties": {
-                "x": { "type": "number" },
-                "y": { "type": "number" }
-              }
-            }
-          }
-        },
-        "elements": {
+        "transform": { "$ref": "#/$defs/transform" },
+        "children": {
           "type": "array",
           "items": {
             "oneOf": [
@@ -215,31 +198,27 @@ PHY (物理配置) → IDX (キー識別) → ELC (電気配線) + MAP (キー
       "visualOffset": { "x": 1, "y": 1, "radius": 1 }
     }
   ],
-  "elements": [
+  "root": [
     {
       "type": "cluster",
       "id": "left_main",
       "name": "Left Main Block",
-      "position": { 
-        "x": 0, "y": 0, 
-        "rotation": 0,
-        "rotationOrigin": { "x": 3, "y": 2 }
-      },
-      "elements": [
+      "transform": { "x": 0, "y": 0, "rotation": 0 },
+      "children": [
         {
           "type": "key",
           "id": "k00",
           "profile": "standard",
-          "position": { "x": 0, "y": 0 },
-          "size": { "width": 1, "height": 1 },
+          "transform": { "x": 0, "y": 0, "rotation": 0 },
+          "size": { "w": 1, "h": 1 },
           "metadata": { "label": "Q" }
         },
         {
           "type": "key", 
           "id": "k01",
           "profile": "standard",
-          "position": { "x": 1, "y": 0 },
-          "size": { "width": 1, "height": 1 },
+          "transform": { "x": 1, "y": 0, "rotation": 0 },
+          "size": { "w": 1, "h": 1 },
           "metadata": { "label": "W" }
         }
       ]
@@ -248,26 +227,22 @@ PHY (物理配置) → IDX (キー識別) → ELC (電気配線) + MAP (キー
       "type": "cluster",
       "id": "left_thumb",
       "name": "Left Thumb Cluster", 
-      "position": { 
-        "x": 2, "y": 3, 
-        "rotation": 15,
-        "rotationOrigin": { "x": 1, "y": 0.5 }
-      },
-      "elements": [
+      "transform": { "x": 2, "y": 3, "rotation": 15 },
+      "children": [
         {
           "type": "key",
           "id": "k30",
           "profile": "standard",
-          "position": { "x": 0, "y": 0 },
-          "size": { "width": 1.25, "height": 1 },
+          "transform": { "x": 0, "y": 0, "rotation": 0 },
+          "size": { "w": 1.25, "h": 1 },
           "metadata": { "label": "Space" }
         },
         {
           "type": "key",
           "id": "k31", 
           "profile": "standard",
-          "position": { "x": 1.25, "y": 0 },
-          "size": { "width": 1, "height": 1 },
+          "transform": { "x": 1.25, "y": 0, "rotation": 0 },
+          "size": { "w": 1, "h": 1 },
           "metadata": { "label": "Enter" }
         }
       ]