diff --git a/.claude/skills/d8d-prototype/steps/step-03-generate-index.md b/.claude/skills/d8d-prototype/steps/step-03-generate-index.md
index 9842995..0bd5a70 100644
--- a/.claude/skills/d8d-prototype/steps/step-03-generate-index.md
+++ b/.claude/skills/d8d-prototype/steps/step-03-generate-index.md
@@ -114,9 +114,10 @@
 
 ```html
 <style>
+    /* phone-frame: iPhone 12+ 逻辑分辨率 390×844，border-box 下 414×868 = 390×844 内容区 + 12px×2 边框 */
     .phone-frame {
-        width: 375px;
-        height: 812px;
+        width: 414px;
+        height: 868px;
         border: 12px solid #1a1a1a;
         border-radius: 40px;
         overflow: hidden;
@@ -127,9 +128,10 @@
         height: 100%;
         border: none;
     }
+    /* grid 列宽 minmax(440px) 容纳 414px phone-frame + 容器内边距 */
     .prototype-grid {
         display: grid;
-        grid-template-columns: repeat(auto-fill, 375px);
+        grid-template-columns: repeat(auto-fill, minmax(440px, 1fr));
         gap: 24px;
         padding: 24px;
         justify-content: center;