通过 div 显示背景图

docs/css/style.css

@@ -24,12 +24,7 @@ html {
 }
 
 body {
-    background-attachment: fixed;
-    background-color: #F9F9F9;
-    background-image: url(../img/Unsplash_V6TWE6h8gyg.jpg);
-    background-position: center;
-    background-repeat: no-repeat;
-    background-size: cover;
+    background-color: #999;
     color: #000;
     cursor: default;
     display: flex;
@@ -216,6 +211,22 @@ footer p {
     width: 1.5em;
 }
 
+/* 背景 */
+
+.page-background {
+    z-index: -100;
+    position: fixed;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100vh;
+    background-attachment: fixed;
+    background-image: url(../img/Unsplash_V6TWE6h8gyg.jpg);
+    background-position: center;
+    background-repeat: no-repeat;
+    background-size: cover;
+}
+
 /* 滚动条 */
 
 ::-webkit-scrollbar {
@@ -243,7 +254,7 @@ footer p {
     left: 0;
     bottom: -110%;
     opacity: 0;
-    transition: all 1.0s;
+    transition: all 0.5s;
 }
 
 .tool-panel-bar {