✅ pass css test

app/static/app.css

@@ -6,23 +6,23 @@ h1 {
   text-align: center;
 }
 
-div.container {
+.container {
   display: flex;
   flex-wrap: wrap;
 }
 
-div.center {
+.center {
   margin: auto;
   max-width: 500px;
 }
 
-a.color {
+.color {
   display: block;
   width: calc(100vw - 24px);
   height: 100px;
   border: 1px solid black;
+  box-sizing: border-box;
   text-align: center;
-    vertical-align: middle;
   line-height: 100px;
   font-size: 18px;
   font-weight: bold;
@@ -31,32 +31,40 @@ a.color {
   border-radius: 12px;
 }
 
-a.red {
-    background-color: #FF0000;
+.red {
+  background-color: #f00;
 }
-a.green {
-    background-color: #00FF00;
+
+.green {
+  background-color: #0f0;
 }
-a.blue {
-    background-color: #0000FF;
-    color: #FFFFFF;
+
+.blue {
+  background-color: #00f;
+  color: #fff;
 }
-a.cyan {
-    background-color: #00FFFF;
+
+.cyan {
+  background-color: #0ff;
 }
-a.yellow {
-    background-color: #FFFF00;
+
+.yellow {
+  background-color: #ff0;
 }
-a.orange {
-    background-color: #FF8000;
+
+.orange {
+  background-color: #ff8000;
 }
-a.purple {
-    background-color: #FF00FF;
+
+.purple {
+  background-color: #f0f;
 }
-a.white {
-    background-color: #FFFFFF;
+
+.white {
+  background-color: #fff;
 }
-a.black {
-    background-color: #000000;
-    color: #FFFFFF;
+
+.black {
+  background-color: #000;
+  color: #fff;
 }