diff --git a/app.py b/app.py
index 0726ef9..2e5a7f6 100644
--- a/app.py
+++ b/app.py
@@ -1,9 +1,12 @@
 #!/usr/bin/env python3
 
+import base64
 import bcrypt
+import hashlib
 import config
 import json
 import re
+import requests
 import schema
 import os
 
@@ -28,10 +31,34 @@ db = client[config.MONGO['database']]
 db.users.create_index('username', unique=True)
 db.songs.create_index('id', unique=True)
 
+
+class HashException(Exception):
+    pass
+
+
 def api_error(message):
     return jsonify({'status': 'error', 'message': message})
 
 
+def generate_hash(id, form):
+    md5 = hashlib.md5()
+    if form['type'] == 'tja':
+        urls = ['%s%s/main.tja' % (config.SONGS_BASEURL, id)]
+    else:
+        urls = []
+        for diff in ['easy', 'normal', 'hard', 'oni', 'ura']:
+            if form['course_' + diff]:
+                urls.append('%s%s/%s.osu' % (config.SONGS_BASEURL, id, diff))
+
+    for url in urls:
+        resp = requests.get(url)
+        if resp.status_code != 200:
+            raise Exception('Invalid response from %s (status code %s)' % (resp.url, resp.status_code))
+        md5.update(resp.content)
+
+    return base64.b64encode(md5.digest())[:-2].decode('utf-8')
+
+
 def login_required(f):
     @wraps(f)
     def decorated_function(*args, **kwargs):
@@ -69,7 +96,8 @@ def get_config():
         'songs_baseurl': config.SONGS_BASEURL,
         'assets_baseurl': config.ASSETS_BASEURL,
         'email': config.EMAIL,
-        'accounts': config.ACCOUNTS
+        'accounts': config.ACCOUNTS,
+        'custom_js': config.CUSTOM_JS
     }
 
     if not config_out.get('songs_baseurl'):
@@ -218,6 +246,14 @@ def route_admin_songs_id_post(id):
     output['preview'] = float(request.form.get('preview')) or None
     output['volume'] = float(request.form.get('volume')) or None
     output['maker_id'] = int(request.form.get('maker_id')) or None
+    output['hash'] = request.form.get('hash')
+
+    if request.form.get('gen_hash'):
+        try:
+            output['hash'] = generate_hash(id, request.form)
+        except HashException as e:
+            flash('An error occurred: %s' % str(e), 'error')
+            return redirect('/admin/songs/%s' % id)
 
     db.songs.update_one({'id': id}, {'$set': output})
     flash('Changes saved.')
diff --git a/config.example.py b/config.example.py
index 1fa4fc7..478aa77 100644
--- a/config.example.py
+++ b/config.example.py
@@ -10,9 +10,12 @@ EMAIL = 'taiko@example.com'
 # Whether to use the user account system.
 ACCOUNTS = True
 
+# Custom JavaScript file to load with the simulator.
+CUSTOM_JS = ''
+
 # MongoDB server settings.
 MONGO = {
-    'host': ['localhost:27017'],
+    'host': ['127.0.0.1:27017'],
     'database': 'taiko'
 }
 
diff --git a/public/src/css/admin.css b/public/src/css/admin.css
index 69bb27c..033bb42 100644
--- a/public/src/css/admin.css
+++ b/public/src/css/admin.css
@@ -131,6 +131,10 @@ h1 small {
     color: white;
 }
 
+.message-error {
+    background: #b92222;
+}
+
 .save-song {
     font-size: 22pt;
     width: 120px;
diff --git a/templates/admin.html b/templates/admin.html
index e92ff9a..6080e06 100644
--- a/templates/admin.html
+++ b/templates/admin.html
@@ -13,7 +13,7 @@
                 <a href="/admin/songs">Songs</a>
             </div>
         </header>
-
+        
         <main>
             <div class="container">
                 {% block content %}{% endblock %}
diff --git a/templates/admin_song_detail.html b/templates/admin_song_detail.html
index 27132f3..9c860ae 100644
--- a/templates/admin_song_detail.html
+++ b/templates/admin_song_detail.html
@@ -1,8 +1,8 @@
 {% extends 'admin.html' %}
 {% block content %}
 <h1>{{ song.title }} <small>(ID: {{ song.id }})</small></h1>
-{% for message in get_flashed_messages() %}
-<div class="message">{{ message }}</div>
+{% for cat, message in get_flashed_messages(with_categories=true) %}
+<div class="message{% if cat %} message-{{cat}}{% endif %}">{{ message }}</div>
 {% endfor %}
 <div class="song-form">
     <form method="post">
@@ -115,6 +115,11 @@
             </select>
         </div>
 
+        <div class="form-field">
+            <p><label for="hash">Hash</label></p>
+            <input type="text" id="hash" value="{{song.hash}}" name="hash"> <span class="checkbox"><input type="checkbox" name="gen_hash" id="gen_hash"{><label for="gen_hash"> Generate</label></span>
+        </div>
+
         <button type="submit" class="save-song">Save</button>
     </form>
     {% if admin.user_level >= 100 %}
@@ -124,3 +129,4 @@
     {% endif %}
 </div>
 {% endblock %}
+