app/templates/application.html.erb
<!DOCTYPE html>
<html lang="en">
<head>
<title>Loading...</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
<link rel="stylesheet" href="/assets/app.css">
</head>
<body>
<%= yield %>
<script src="/assets/app.js"></script>
</body>
</html>