some minor syntax corrections and a rewrite of the demo index.html and css file

css/css.css

@@ -7,26 +7,17 @@ body {
 	display: flex;
 	justify-content:center;
 	align-items:center;
+	flex-direction: column;
 }
 
-#disc {
+.bui_window_content {
 	display:block;
-	width:80%;
-	min-height:60%;
 	text-align:center;
+	padding: 5px;
+	
 }
 
-.library {
-	background: rgba(200,200,200,1);
-	text-align:left;
-	margin:5px 5px -15px 5px;
-	padding:5px 5px 20px 5px;
-	min-height:10%;
-	border:solid 1px rgba(140,140,140,1);
-	border-radius:10px 10px 0px 0px;
-}
-
-.button {
+.bui_button_root {
 	display: inline-block;
 	background: rgba(150,150,150,0.7);
 	user-select: none;
@@ -37,9 +28,24 @@ body {
 	cursor:pointer;
 }
 
-.button:hover {
+.bui_button_root:hover {
 	background: rgba(140,140,140,1);
 	margin:0px;
 	padding:3px;
 	transition:0.2s;
 }
+
+.bui_window_root {
+	position: relative;
+	background: rgba(200,200,200,1);
+	color: black;
+	border: solid 1px rgba(140,140,140,1);
+	border-radius: 5px;
+}
+
+.bui_window_titlebar {
+	display: flex;
+	justify-content: space-between;
+	background: rgba(100,100,100,1);
+	padding: 5px;
+}