diff --git a/client.js b/client.js
index 25233b6..2e9481b 100644
--- a/client.js
+++ b/client.js
@@ -1,3 +1,20 @@
+import mermaid from 'https://cdn.jsdelivr.net/npm/mermaid@10/dist/mermaid.esm.min.mjs'
+
+let lastDiagram = ''
+let rendering = false
+let theme = 'dark'
+
+function setTheme(lightMatches) {
+	theme = lightMatches ? 'default' : 'dark'
+	mermaid.initialize({ startOnLoad: true, theme })
+	renderLastDiagram()
+}
+if (window.matchMedia) {
+	let lightMatcher = window.matchMedia('(prefers-color-scheme: light)')
+	lightMatcher.addEventListener('change', ({ matches }) => setTheme(matches))
+	setTheme(lightMatcher.matches)
+}
+
 let connectionAttempt = 0
 function connectSocket() {
 	const socket = new WebSocket('ws://localhost:8080')
@@ -6,14 +23,44 @@ function connectSocket() {
 	})
 	socket.addEventListener('close', () => {
 		connectionAttempt += 1
-		setTimeout(connectSocket(), 1000)
+		setTimeout(() => requestAnimationFrame(connectSocket), 1000)
 	})
 	socket.addEventListener('message', handleMessage)
 }
 
-function handleMessage({ data }) {
-	console.log({ data })
-	if (data == 'reload') window.location.reload()
+async function handleMessage({ data }) {
+	if (data == 'hi') {
+		console.log('👋')
+	} else if (data == 'reload') {
+		window.location.reload()
+	} else {
+		try {
+			await handleStructuredMessage(JSON.parse(data))
+		} catch (err) {
+			console.error(`failed to process structured websocket message: ${err}`)
+		}
+	}
+}
+
+async function handleStructuredMessage(data) {
+	switch (data.type) {
+		case 'mermaid': {
+			if (rendering) return
+			rendering = true
+
+			lastDiagram = data.contents
+			await renderLastDiagram()
+
+			rendering = false
+			break
+		}
+	}
+}
+
+async function renderLastDiagram() {
+	if (lastDiagram == '') return
+	document.getElementById('diagram').innerHTML =
+		(await mermaid.render('mermaid', lastDiagram)).svg
 }
 
 addEventListener('DOMContentLoaded', connectSocket)
diff --git a/mod.ts b/mod.ts
index 51aa980..d02f762 100755
--- a/mod.ts
+++ b/mod.ts
@@ -54,41 +54,60 @@ const command = new Command()
 
 async function openBrowser(args: Args): Promise<void> {
 	if (args.open) {
+		// TODO: this is broken?
 		const url = `http://${args.host}:${args.port}`
 		console.log(`opening browser to ${url}`)
 		const process = new Deno.Command('xdg-open', {
 			args: [url],
 		}).spawn()
-
-		// const result = true
 		console.log(`opened browser to ${url}: ${await process.status}`)
 	}
 }
 
 async function runServer(args: Args): Promise<void> {
 	const opts = { hostname: args.host, port: args.port }
-	Deno.serve(opts, async (req: Request) => {
+	await Deno.serve(opts, async (req: Request, info: Deno.ServeHandlerInfo) => {
 		if (req.headers.get('upgrade') == 'websocket') {
-			return handleWebSocket(req)
+			return handleWebSocket(req, info)
 		}
 
 		const url = new URL(req.url)
 		if (url.pathname == '/client.js') {
 			return new Response(await Deno.readTextFile('./client.js'), {
-				headers: new Headers({ 'content-type': 'text/javascript' }),
+				headers: new Headers({
+					'content-type': 'text/javascript;charset=UTF-8',
+				}),
 			})
 		} else if (url.pathname == '/') {
-			return new Response(html.index, {
-				headers: new Headers({ 'content-type': 'text/html' }),
+			return new Response(page(null, await listDiagramsHtml(args.input)), {
+				headers: new Headers({ 'content-type': 'text/html', charset: 'utf-8' }),
 			})
+		} else {
+			const file = url.pathname.replaceAll('..', '')
+			if (file.endsWith('.mmd')) {
+				if (req.headers.get('accepts') == 'text/mermaid') {
+					return new Response(Deno.readTextFileSync(file), {
+						headers: { 'content-type': 'text/mermaid' },
+					})
+				}
+
+				return new Response(
+					page(
+						url.pathname,
+						await diagramContent(args, url.pathname.replaceAll('..', '')),
+					),
+					{
+						headers: new Headers({
+							'content-type': 'text/html',
+							charset: 'utf-8',
+						}),
+					},
+				)
+			}
 		}
 
 		return new Response(`Hello, ${url.pathname}!`)
-	})
-
-	return await new Promise((_resolve) => {
-		// a promise that never resolves
-	})
+	}).finished
 }
 
 async function runMermaidFileWatcher(args: Args) {
@@ -102,7 +121,6 @@ async function runMermaidFileWatcher(args: Args) {
 		for (const p of paths) {
 			console.log(p)
 			if (p.endsWith('.mmd') && (kind == 'create' || kind == 'modify')) {
-				console.log('omg a mermaid')
 				const contents = await Deno.readTextFile(p)
 				sockets.forEach((s) =>
 					s.send(JSON.stringify({ type: 'mermaid', contents }))
@@ -113,17 +131,17 @@ async function runMermaidFileWatcher(args: Args) {
 	}
 }
 
-function handleWebSocket(req: Request): Response {
+function handleWebSocket(req: Request, info: Deno.ServeHandlerInfo): Response {
 	const { socket, response } = Deno.upgradeWebSocket(req)
 
 	socket.addEventListener('open', (_ev) => {
-		console.log(`websocket open`)
+		console.log(`websocket open from ${JSON.stringify(info.remoteAddr)}`)
 		socket.send('hi')
 		sockets.add(socket)
 	})
 
 	socket.addEventListener('message', (ev) => {
-		console.log(`websocket message: ${ev}`)
+		console.log(`websocket message: ${JSON.stringify(ev)}`)
 		try {
 			if (ev.data) {
 				const data = JSON.parse(ev.data)
@@ -136,7 +154,7 @@ function handleWebSocket(req: Request): Response {
 	})
 
 	socket.addEventListener('close', (ev) => {
-		console.log(`websocket close: ${ev}`)
+		console.log(`websocket close: ${JSON.stringify(ev)}`)
 		sockets.delete(socket)
 	})
 
@@ -151,17 +169,52 @@ function handleClientEvent(socket: WebSocket, ce: ClientEvent) {
 	}
 }
 
-const html = {
-	index: `
-		<!DOCTYPE html>
-		<h1>Hello, index!</h1>
-		<script src="./client.js"></script>
-		<script src="https://cdn.jsdelivr.net/npm/mermaid@10.9.1/dist/mermaid.min.js"></script>
-	`,
+const listDiagramsHtml = async (dir: string): Promise<string> => {
+	const list = []
+	for await (const entry of Deno.readDir(dir)) {
+		if (entry.isFile && entry.name.endsWith('.mmd')) {
+			list.push(`<li><a href="/${entry.name}">${entry.name}</a></li>`)
+		}
+	}
+	return `<ul>${list.join('\n')}</ul>`
 }
 
+const diagramContent = async (args: Args, file: string): Promise<string> => {
+	let content = await Deno.readTextFile(args.input + file)
+	return `<div id="diagram" class="mermaid">${content}</div>`
+}
+
+const page = (title: string | null, content: string) =>
+	`<!DOCTYPE html>
+<html>
+<head>
+	<meta charset="utf-8">
+	<meta viewport="">
+	<title>${title !== null ? `${title} - ` : ''}Diagram</title>
+</head>
+<body>
+	<h1><a href="/">Diagram Index</a>${
+		title !== null ? ` <a href="${title}">${title}</a>` : ''
+	}</h1>
+  <script type="module" src="./client.js"></script>
+	${content}
+	<style>
+		@media (prefers-color-scheme: dark) {
+			:root {
+				--bg: #111111;
+				--text: #ffffff;
+			}
+		}
+
+		body {
+			background-color: var(--bg);
+			color: var(--text);
+		}
+	</style>
+</body>
+</html>`
+
 async function run(args: Args) {
-	// TODO: start mermaid file watcher
 	await Promise.all([
 		runMermaidFileWatcher(args),
 		runServer(args),