diff --git a/vweb/src/highlighted_line.jsx b/vweb/src/highlighted_line.jsx
new file mode 100644
index 0000000..42c91f7
--- /dev/null
+++ b/vweb/src/highlighted_line.jsx
@@ -0,0 +1,118 @@
+import React from 'react'
+
+const keywords = {
+    '.db': 'directive',
+    '.org': 'directive',
+    '.equ': 'directive',
+    '#if': 'macro',
+    '#unless': 'macro',
+    '#while': 'macro',
+    '#until': 'macro',
+    '#do': 'macro',
+    '#else': 'macro',
+    '#end': 'macro'
+}
+
+export default function({ line }) {
+    let remainder = line.trim(), // The part of the line we haven't processed
+        current = '', // The characters that aren't part of a recognized token that we're building up
+        idx = 0, // A counter for unique keys
+        label_directive = false // Whether this line has a label definition or directive on it
+    const tokens = [] // The list of spans we're building up
+
+    // Push a span containing the "current" string
+    const pushCurrent = () => {
+        if (current !== '') { tokens.push(<span key={`token-${idx++}`}>{current}</span>) }
+        current = ''
+    }
+
+    // Push a recognized token with a classname
+    const pushToken = (css, tok) => {
+        pushCurrent()
+        tokens.push(<span className={css} key={`token-${idx++}`}>{tok}</span>)
+        remainder = remainder.slice(tok.length)
+    }
+
+    // Consume things from the remainder of the line. The general idea here is that we look at the start of the str
+    // and see if it's a recognizable token. If not, add a single char to `current` and keep going. If so, then push
+    // `current`, push that token, and keep going.
+    // This works but only just: everything we highlight (directives, macros, label _declarations,_ numbers, strings,
+    // and comments) is recognizable that way and can't be a substring of anything else. We could not, for example,
+    // recognize label _usages_ this way because we can't tell from the first character that it is one
+    while (remainder !== '') {
+        let any = false // Whether any special thing matched
+
+        if (remainder[0] === ';') { // If it's a comment, consume the rest
+            pushToken('comment', remainder)
+            remainder = ''
+            any = true
+        }
+
+        if (remainder[0] === '"') { // Is it a string?
+            let [str, newRemainder] = readQuotedString(remainder)
+            pushToken('string', str)
+            remainder = newRemainder
+            any = true
+        }
+
+        // Try to match number patterns
+        const num = remainder.match(/^(0x[0-9a-fA-F]+)/) ||
+            remainder.match(/^(0b[10]+)/) ||
+            remainder.match(/^(-?\d+)/)
+        if (num && num[1]) { // Is it a number?
+            pushToken('number', num[1])
+            any = true
+        }
+
+        // Any sort of keyword?
+        Object.keys(keywords).forEach((keyword) => {
+            if (remainder.startsWith(keyword)) {
+                pushToken(keywords[keyword], keyword)
+                label_directive = true
+                any = true
+            }
+        })
+
+        // Labels!
+        const lbl = remainder.match(/^([a-zA-Z\d_$]+:)/)
+        if (lbl && lbl[1]) {
+            pushToken('label', lbl[1])
+            any = true
+            label_directive = true
+        }
+
+        if (!any) { // Nothing better matched, eat a char and keep going
+            current += remainder[0]
+            remainder = remainder.slice(1)
+        }
+    }
+
+    pushCurrent()
+
+    return <>{label_directive ? '' : <>&nbsp;&nbsp;</>}{tokens}</>
+}
+
+// A cheap way to indent lines: if the first token is a macro, directive, or label declaration, indent it two spaces
+export function indent(str) {
+    str = str.trim()
+    if (str.match(/^#[a-z]+/) ||
+        str.match(/^\.[a-z]+/) ||
+        str.match(/^[a-zA-Z\d]+:/)) {
+        return str
+    } else {
+        return '  ' + str
+    }
+}
+
+// If the start of this line is a quoted string, return that + the remainder (in an escape-aware way). Otherwise
+// just return empty string + the entire line
+function readQuotedString(line) {
+    if (line[0] === '"') {
+        for (let n = 1; n < line.length; n++) {
+            if (line[n] === '"' && line[n-1] !== '\\') {
+                return [line.slice(0, n+1), line.slice(n+1)]
+            }
+        }
+    }
+    return ['', line]
+}
\ No newline at end of file
diff --git a/vweb/src/snippet_emulator.css b/vweb/src/snippet_emulator.css
index a04bafb..105c88c 100644
--- a/vweb/src/snippet_emulator.css
+++ b/vweb/src/snippet_emulator.css
@@ -52,4 +52,11 @@ body {
 .snippetEmulator .reset { color: lightcoral }
 .snippetEmulator .build, .snippetEmulator .edit { color: dodgerblue }
 .snippetEmulator .highlight { background-color: darkgoldenrod }
-.snippetEmulator .src { overflow: scroll }
\ No newline at end of file
+.snippetEmulator .src { overflow: scroll }
+
+.snippetEmulator .src .directive { color: darkcyan }
+.snippetEmulator .src .macro { color: mediumpurple }
+.snippetEmulator .src .number { color: lightskyblue }
+.snippetEmulator .src .string { color: darkseagreen }
+.snippetEmulator .src .label { color: chocolate }
+.snippetEmulator .src .comment { color: grey }
\ No newline at end of file
diff --git a/vweb/src/snippet_emulator.jsx b/vweb/src/snippet_emulator.jsx
index 393433e..3aaf09d 100644
--- a/vweb/src/snippet_emulator.jsx
+++ b/vweb/src/snippet_emulator.jsx
@@ -1,8 +1,9 @@
 import './snippet_emulator.css'
-import React, {useState, useCallback, useEffect} from 'react'
-import {WasmCPU, assemble_snippet, source_map, NovaForth} from '../pkg/vweb.js'
+import React, { useState, useCallback, useEffect } from 'react'
+import { WasmCPU, assemble_snippet, source_map } from '../pkg/vweb.js'
+import HighlightedLine, { indent } from './highlighted_line'
 
-export default function({ children }) {
+export default function({ children, width = 20 }) {
     // Use this by giving it some source as a body:
     // <SnippetEmulator>
     //   {`.org 0x400
@@ -80,7 +81,7 @@ export default function({ children }) {
     // On load, clean the source and build the stuff
     useEffect(() => {
         const lines = React.Children.toArray(children)[0].split('\n')
-        const cleaned = lines.map(l => l.trim()).join('\n')
+        const cleaned = lines.map(indent).join('\n')
         setSrc(cleaned)
         rebuild(cleaned)
     }, [children])
@@ -95,7 +96,7 @@ export default function({ children }) {
 
     if (editing) {
         return (
-            <div className='snippetEmulator'>
+            <div className='snippetEmulator' style={{ gridTemplateColumns: `${width}em` }}>
                 <textarea value={src} onChange={onChangeSrc}></textarea>
                 <div className='message'>{message}</div>
                 <div className='buttons'>
@@ -105,7 +106,7 @@ export default function({ children }) {
         )
     } else {
         return (
-            <div className='snippetEmulator'>
+            <div className='snippetEmulator' style={{ gridTemplateColumns: `${width}em` }}>
                 <SourceDisplay src={src} activeLine={activeLine}/>
                 <div className='message'>{message}</div>
                 <div className='buttons'>
@@ -124,7 +125,11 @@ function SourceDisplay({ src, activeLine }) {
     const lines = src.split('\n')
     const lineDivs = lines.map((line, i) => {
         // Loop indices are from 0, activeLine numbers are from 1
-        return (<div key={`line_${i}`} className={i + 1 === activeLine ? 'highlight' : ''}>{line || <>&nbsp;</>}</div>)
+        return (
+            <div key={`line_${i}`} className={i + 1 === activeLine ? 'highlight' : ''}>
+                {<HighlightedLine line={line}/> || <>&nbsp;</>}
+            </div>
+        )
     })
     return (
         <div className='src'>{lineDivs}</div>
diff --git a/vweb/src/snippet_emulator_demo.html b/vweb/src/snippet_emulator_demo.html
index 06c9ccc..109a7ba 100644
--- a/vweb/src/snippet_emulator_demo.html
+++ b/vweb/src/snippet_emulator_demo.html
@@ -15,13 +15,15 @@
         Quisque tristique diam et purus sagittis, posuere pharetra orci egestas. Praesent imperdiet sapien vel fermentum
         pulvinar. Nulla ac tortor laoreet, fringilla tellus nec, ullamcorper mi.
     </p>
-    <div class="snippet">
+    <div class="snippet" data-width="30">
         <pre>
         .org 0x400
-        push 0
-        blah: add 1
-        jmp $-1
-        hlt
+            push 0 ; A comment
+        blah:
+            add 1
+            jmp $-1
+            hlt
+        .db "A string; \"semicolon-y\"\0"
         </pre>
     </div>
     <p>
diff --git a/vweb/src/snippet_emulator_demo.jsx b/vweb/src/snippet_emulator_demo.jsx
index f35b922..3669628 100644
--- a/vweb/src/snippet_emulator_demo.jsx
+++ b/vweb/src/snippet_emulator_demo.jsx
@@ -6,7 +6,8 @@ import init, { WasmCPU, assemble_snippet } from '../pkg/vweb.js'
 document.addEventListener('DOMContentLoaded', () => {
     init().then(() => {
         document.querySelectorAll('.snippet').forEach((el) => {
-            createRoot(el).render(React.createElement(SnippetEmulator, { children: el.innerText }))
+            const props = { children: el.innerText, width: el.getAttribute('data-width') }
+            createRoot(el).render(React.createElement(SnippetEmulator, props))
         })
     })
 })
\ No newline at end of file