diff --git a/index.html b/index.html
index f7cebb8..e4c6d12 100644
--- a/index.html
+++ b/index.html
@@ -117,6 +117,18 @@
             border: 5px solid #fff;
             box-shadow: 0 0 10px rgba(0, 0, 0, 0.8);
         }
+#expanded-card {
+    width: 90vw;         /* 画面幅の90%までに制限 */
+    max-width: none;     /* 上限幅の制限を解除 */
+    height: auto;
+    top: 50%;
+    left: 50%;
+    transform: translate(-50%, -50%);
+    border: 5px solid #fff;
+    box-shadow: 0 0 10px rgba(0, 0, 0, 0.8);
+    background-color: #fff;
+    z-index: 1000;
+}
 
      
         #how-to-play {