diff --git a/src/run-web.html b/src/run-web.html
new file mode 100644
index 0000000..7d86e72
--- /dev/null
+++ b/src/run-web.html
@@ -0,0 +1 @@
+<!doctype html><html><head><meta charset="utf8"><title>uw8-run</title><style>body,canvas,html{background-color:#202024;margin:0;padding:0}body,html{height:100%}body{display:grid;grid-template-rows:1fr}#screen{align-self:center;border:4px solid #303040;image-rendering:pixelated;justify-self:center}#message{background-color:rgba(0,0,0,.4);color:#c64;font:700 12pt sans-serif;padding:8px;position:absolute;width:calc(100% - 16px);z-index:2}@media (min-width:648px) and (min-height:488px){#screen{height:480px;width:640px}}@media (min-width:968px) and (min-height:728px){#screen{height:720px;width:960px}}</style></head><body> <canvas id="screen" width="320" height="240" tabindex="1"> </canvas> <div id="message"></div> </body><script type="module">function e(e){return e&&e.__esModule?e.default:e}let A=function(A,t={}){t.setMessage||(t.setMessage=(e,A)=>{A&&console.log("error: "+A)});let r,B,a,n,o=A.getContext("2d"),s=o.createImageData(320,240),i=t.devkitMode,F=e=>new Uint8Array(e),l=e=>new 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Blob(e,{type:"video/webm"}),".webm")},a.start(),n=Date.now(),setTimeout(B,1e3)}(),e.preventDefault()}o?Q|=r:Q&=~r};E.onkeydown=e,E.onkeyup=e}async function g(a,n){r&&(r(),r=null);let E=a.byteLength;if(t.setMessage(E),0==E)return;B=a;let c=window.location.pathname;if(E<=1024&&!n){let e="";for(let A of F(a))e+=String.fromCharCode(A);c+="#"+btoa(e),c!=window.location.pathname+window.location.hash&&history.pushState(null,null,c)}A.width=A.width;try{let A={initial:4};i||(A.maximum=4);let n,c=new WebAssembly.Memory({initial:4,maximum:i?16:4}),I=F(c.buffer),f={env:{memory:c}},d=e=>{if(n&&(!i||0!=F(e)[0])){I.set(F(e));let A=n.exports.load_uw8(e.byteLength);e=new ArrayBuffer(A),F(e).set(I.slice(0,A))}return e},w=async e=>(await WebAssembly.instantiate(e,f)).instance,C=async e=>w(d(await(await fetch(e)).arrayBuffer()));n=await 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e in y.exports)f.env[e]=y.exports[e];let u=await w(a),h=l(s.data.buffer),b=Date.now(),k=!0;r=()=>k=!1;const D=1e3/60;let m=b;!function e(){if(k)try{let A=Date.now(),t=!1;if(A>=m){let e=navigator.getGamepads(),r=0;for(let A=0;A<4;++A){let B=e[A];if(B){for(let e=0;e<8;++e){let t=(e+12)%16;B.buttons.length>t&&B.buttons[t].pressed&&(r|=1<<8*A+e)}if(B.axes.length>1)for(let e=0;e<4;++e){let t=B.axes[1-(e>>1)];(1&e?t:-t)>.5&&(r|=1<<8*A+e)}B.buttons.length>9&&B.buttons[9].pressed&&(t=!0)}}let B=l(c.buffer);B[16]=A-b,B[17]=Q|r,u.exports.upd(),y.exports.endFrame();let a=l(c.buffer.slice(77824,78848));for(let e=0;e<76800;++e)h[e]=4278190080|a[I[e+120]];o.putImageData(s,0,0),m=Math.max(m+D,A)}t?g(B):window.requestAnimationFrame(e)}catch(e){t.setMessage(E,e.toString())}}()}catch(e){t.setMessage(E,e.toString())}}function c(e,A){let t=document.createElement("a");t.href=URL.createObjectURL(e),t.download="microw8_"+(new Date).toISOString()+A,t.click(),URL.revokeObjectURL(t.href)}return{runModule:g,runModuleFromURL:async function(e,A){let t=await fetch(e),r=t.headers.get("Content-Type");if(r&&r.includes("html"))throw!1;g(await t.arrayBuffer(),A||i)},setDevkitMode:e=>i=e}}(document.getElementById("screen"),{setMessage:(e,A)=>{let t=document.getElementById("message");A&&(t.innerText=A),t.hidden=!A}});new EventSource("events").onmessage=e=>{console.log(e.data),"L"==e.data&&A.runModuleFromURL("cart",!0)},A.runModuleFromURL("cart",!0);</script></html>
\ No newline at end of file
diff --git a/web/build-run-web b/web/build-run-web
new file mode 100755
index 0000000..cc0cc6d
--- /dev/null
+++ b/web/build-run-web
@@ -0,0 +1,2 @@
+#!/bin/bash
+rm -rf .parcel-cache && yarn parcel build src/run-web.html && cp dist/run-web.html ../src/
diff --git a/web/src/run-web.css b/web/src/run-web.css
new file mode 100644
index 0000000..ca6d48e
--- /dev/null
+++ b/web/src/run-web.css
@@ -0,0 +1,46 @@
+html, body, canvas {
+    padding: 0;
+    margin: 0;
+    background-color: #202024;
+}
+
+html {
+    height: 100%;
+}
+
+body {
+    height: 100%;
+    display: grid;
+    grid-template-rows: 1fr;
+}
+
+#screen {
+    align-self: center;
+    justify-self: center;
+    image-rendering: pixelated;
+    border: 4px solid #303040;
+}
+
+#message {
+    position: absolute;
+    width: calc(100% - 16px);
+    background-color: rgba(0, 0, 0, 0.4);
+    color: #c64;
+    padding: 8px;
+    font: bold 12pt sans-serif;
+    z-index: 2;
+}
+
+@media (min-width: 648px) and (min-height: 488px) {
+    #screen {
+        width: 640px;
+        height: 480px;
+    }
+}
+
+@media (min-width: 968px) and (min-height: 728px) {
+    #screen {
+        width: 960px;
+        height: 720px;
+    }
+}
diff --git a/web/src/run-web.html b/web/src/run-web.html
index 666cf0e..9799736 100644
--- a/web/src/run-web.html
+++ b/web/src/run-web.html
@@ -3,10 +3,14 @@
     <head>
         <meta charset="utf8" />
         <title>uw8-run</title>
+        <style>
+            @import "run-web.css";
+        </style>
     </head>
     <body>
-        <canvas id="screen" width="320" height="240">
+        <canvas id="screen" width="320" height="240" tabindex="1">
         </canvas>
+        <div id="message"></div>
     </body>
     <script type="module">
         import "./run-web.js";
diff --git a/web/src/run-web.js b/web/src/run-web.js
index 89817fd..6f1c552 100644
--- a/web/src/run-web.js
+++ b/web/src/run-web.js
@@ -1,6 +1,14 @@
 import MicroW8 from './microw8.js';
 
-let uw8 = MicroW8(document.getElementById('screen'));
+let uw8 = MicroW8(document.getElementById('screen'), {
+    setMessage: (_, err) => {
+        let elem = document.getElementById('message');
+        if(err) {
+            elem.innerText = err;
+        }
+        elem.hidden = !err;
+    }
+});
 let events = new EventSource('events');
 events.onmessage = event => {
     console.log(event.data);
