调整

liuwenai · liuwenai · commit b8129933e7b6 · 2020-04-17T16:26:34.000+08:00
diff --git a/README.md b/README.md
@@ -245,10 +245,31 @@ HTML **超文本标记语言**
   #### 拖拽元素
 
     页面设置了`draggable = 'true'`属性元素
-    
+
+     + `ondragstart` 拖拽开始时调用
+     + `ondragleave` **鼠标离开拖拽元素时**调用
+     + `ondragend` 拖拽结束时
+     + `ondrag` 整个拖拽过程都会调用
+
 
     ```html
         <div class="box" draggable="true"></div>
     ```
+
+    CSS
+
+    #### background的常见背景属性
+
+    + `background-color:#ff99ff`，设置元素的背景色
+    + `background-image:url(https://github.com/images/2.gif)`，图像设置成背景
+    + `background-repeat:no-repeat`，是否平铺
+        - `no-repeat` 不要平铺
+        - `repeat-x` 横向平铺
+        - `repeat-y` 纵向平铺
+    + `background-position`，背景定位
+    ....
+
+    #### ID选择器：规定用`#`来定义
+
     
 
diff --git a/background.html b/background.html
@@ -0,0 +1,84 @@
+<!DOCTYPE html>
+<html>
+<head lang="en">
+    <meta charset="UTF-8">
+    <title></title>
+    <style>
+        div {
+            width: 500px;
+            height: 100px;
+            margin: 10px auto;
+            border: 1px solid #000;
+        }
+
+        /* 语法：
+            linear-gradient(方向，起始颜色，终止颜色);
+            方向：to left   to right  to top   to bottom 　角度　30deg
+            起始颜色
+            终止颜色
+        */
+        div:nth-child(1) {
+            background-image: linear-gradient(to right, yellow, green);
+        }
+
+        /* 不写方向，表示默认的方向是：从上往下 */
+        div:nth-child(2) {
+            background-image: linear-gradient(yellow, green);
+        }
+
+        /* 方向可以指定角度 */
+        div:nth-child(3) {
+            width: 100px;
+            height: 100px;
+            background-image: linear-gradient(135deg, yellow, green);
+        }
+
+        /* 0%的位置开始出现黄色，40%的位置开始出现红色的过度。70%的位置开始出现绿色的过度，100%的位置开始出现蓝色 */
+        div:nth-child(4) {
+            background-image: linear-gradient(to right,
+            yellow 0%,
+            red 40%,
+            green 70%,
+            blue 100%);
+
+        }
+
+        /* 颜色之间，出现突变 */
+        div:nth-child(5) {
+            background-image: linear-gradient(45deg,
+            yellow 0%,
+            yellow 25%,
+            blue 25%,
+            blue 50%,
+            red 50%,
+            red 75%,
+            green 75%,
+            green 100%
+            );
+        }
+
+        div:nth-child(6) {
+            background-image: linear-gradient(to right,
+            #000 0%,
+            #000 25%,
+            #fff 25%,
+            #fff 50%,
+            #000 50%,
+            #000 75%,
+            #fff 75%,
+            #fff 100%
+            );
+
+        }
+
+    </style>
+</head>
+<body>
+<div></div>
+<div></div>
+<div></div>
+<div></div>
+<div></div>
+<div></div>
+</body>
+</html>
