Opa拥有简洁、简单、可复用等特点。而且还极其强大，支持高并发、动态分布，极其安全。Opa设计让Web开发变得更加有乐趣，安全并且是正确的选择。 它需要64位的平台支持。

type message = { author : string ; text : string }

@publish room = Network.cloud("room") : Network.network(message)

user_update(x : message) =

line = <div class="line">

<div class="user">{x.author}:</>

<div class="message">{x.text}</>

</>

do Dom.transform([#conversation +<- line ])

Dom.scroll_to_bottom(#conversation)

broadcast(author) =

do Network.broadcast({~author text=Dom.get_value(#entry)}, room)

Dom.clear_value(#entry)

start() =

author = Random.string(8)

<div id=#header><div id=#logo></></>

<div id=#conversation onready={_ -> Network.add_callback(user_update, room)}></>

<div id=#footer>

<input id=#entry onnewline={_ -> broadcast(author)} />

<div class="button" onclick={_ -> broadcast(author)}>Post</>

</>

server = Server.one_page_bundle("Chat", [@static_resource_directory("resources")],

["resources/css.css"], start)