GUI base navigation & home

theseus_gui/src/app.html

@@ -5,7 +5,7 @@
 		<meta name="viewport" content="width=device-width, initial-scale=1" />
 		%svelte.head%
 	</head>
-	<body>
-		<div>%svelte.body%</div>
+	<body style="background-color: hsl(220, 13%, 15%)">
+		%svelte.body%
 	</body>
 </html>