Improve CSS formatting and update circle dimensions

- Added spaces after colons in `.blue` and `.circle` classes for better readability and consistency.
- Updated `.circle` dimensions from `300px` to `500px` for larger display.

Author: dzungluong

style.css

@@ -1,8 +1,9 @@
 .blue {
-			background-color:blue
+	background-color: blue
 }
-.circle{
-			border-radius:50%;
-			width:300px;
-			height:300px;
+
+.circle {
+	border-radius: 50%;
+	width: 500px;
+	height: 500px;
 }