✅ pass css test

app/static/app.css

@@ -1,62 +1,70 @@
 html {
-    font-family: sans-serif;
+  font-family: sans-serif;
 }
 
 h1 {
-    text-align: center;
+  text-align: center;
 }
 
-div.container {
-    display: flex;
-    flex-wrap: wrap;
+.container {
+  display: flex;
+  flex-wrap: wrap;
 }
 
-div.center {
-    margin: auto;
-    max-width: 500px;
+.center {
+  margin: auto;
+  max-width: 500px;
 }
 
-a.color {
-    display: block;
-    width: calc(100vw - 24px);
-    height: 100px;
-    border: 1px solid black;
-    text-align: center;
-    vertical-align: middle;
-    line-height:100px;
-    font-size:18px;
-    font-weight: bold;
-    cursor: pointer;
-    margin-bottom: 16px;
-    border-radius: 12px;
+.color {
+  display: block;
+  width: calc(100vw - 24px);
+  height: 100px;
+  border: 1px solid black;
+  box-sizing: border-box;
+  text-align: center;
+  line-height: 100px;
+  font-size: 18px;
+  font-weight: bold;
+  cursor: pointer;
+  margin-bottom: 16px;
+  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;
 }