change background use rgba mode.

Author: JebySun

index.html

@@ -22,8 +22,7 @@
             top: 50%;
             margin-left:-400px; 
             margin-top: -80px;
-			background-color:#000000;
-			opacity:0.5;
+			background-color:rgba(0, 0, 0, 0.75);
 		}
 		#container p{
 			font-size:36px;