修改遮罩

src/components/course/course-covers.vue

@@ -49,14 +49,11 @@ export default {
 .course-covers-wrapper {
   display: flex;
   flex-direction: column;
-  left: 0;
-  top: 50%;
   width: 100%;
-  height: 210px;
+  height: 100%;
   background: rgba(0, 0, 0, 0.8);
   justify-content: center;
   align-content: center;
-  transform: translate3d(0, -50%, 0);
   .tips {
     display: inline-block;
     margin-bottom: 15px;