diff --git a/.gcloudignore b/.gcloudignore
new file mode 100644
index 0000000..603f0b6
--- /dev/null
+++ b/.gcloudignore
@@ -0,0 +1,19 @@
+# This file specifies files that are *not* uploaded to Google Cloud
+# using gcloud. It follows the same syntax as .gitignore, with the addition of
+# "#!include" directives (which insert the entries of the given .gitignore-style
+# file at that point).
+#
+# For more information, run:
+#   $ gcloud topic gcloudignore
+#
+.gcloudignore
+# If you would like to upload your .git directory, .gitignore file or files
+# from your .gitignore file, remove the corresponding line
+# below:
+.git
+.gitignore
+
+# Python pycache:
+__pycache__/
+# Ignored by the build system
+/setup.cfg
\ No newline at end of file
diff --git a/app.yaml b/app.yaml
index 17e7bfd..9ec526f 100644
--- a/app.yaml
+++ b/app.yaml
@@ -1,8 +1,7 @@
-runtime: python27
-api_version: 1
-threadsafe: true
+runtime: python312
+app_engine_apis: true
+entrypoint: gunicorn -b :$PORT main:app
 
-# [START handlers]
 handlers:
 - url: /favicon\.ico
   static_files: favicon.ico
@@ -12,13 +11,8 @@ handlers:
   static_dir: bootstrap
 
 - url: /.*
-  script: guestbook.app
-# [END handlers]
+  script: auto
 
-# [START libraries]
-libraries:
-- name: webapp2
-  version: latest
-- name: jinja2
-  version: latest
-# [END libraries]
+automatic_scaling:
+  min_instances: 0
+  max_instances: 1
diff --git a/main.py b/main.py
new file mode 100644
index 0000000..09fbb62
--- /dev/null
+++ b/main.py
@@ -0,0 +1,72 @@
+import os
+import urllib.parse
+
+from flask import Flask, render_template, request, redirect
+from google.appengine.api import users, wrap_wsgi_app
+from google.cloud import ndb
+
+app = Flask(__name__)
+app.wsgi_app = wrap_wsgi_app(app.wsgi_app)
+client = ndb.Client()
+
+DEFAULT_GUESTBOOK_NAME = 'default_guestbook'
+
+def guestbook_key(guestbook_name=DEFAULT_GUESTBOOK_NAME):
+    return ndb.Key('Guestbook', guestbook_name)
+
+class Author(ndb.Model):
+    identity = ndb.StringProperty()
+    email = ndb.StringProperty()
+
+class Greeting(ndb.Model):
+    author = ndb.StructuredProperty(Author)
+    content = ndb.StringProperty()
+    date = ndb.DateTimeProperty(auto_now_add=True)
+
+@app.route('/')
+def main_page():
+    guestbook_name = request.args.get('guestbook_name', DEFAULT_GUESTBOOK_NAME)
+    
+    with client.context():
+        greetings_query = Greeting.query(
+            ancestor=guestbook_key(guestbook_name)).order(-Greeting.date)
+        greetings = greetings_query.fetch(10)
+
+    user = users.get_current_user()
+    if user:
+        url = users.create_logout_url(request.url)
+        url_linktext = 'Logout'
+    else:
+        url = users.create_login_url(request.url)
+        url_linktext = 'Login'
+
+    template_values = {
+        'user': user,
+        'greetings': greetings,
+        'guestbook_name': urllib.parse.quote_plus(guestbook_name),
+        'url': url,
+        'url_linktext': url_linktext,
+    }
+
+    return render_template('index.html', **template_values)
+
+@app.route('/sign', methods=['POST'])
+def sign_guestbook():
+    guestbook_name = request.args.get('guestbook_name', DEFAULT_GUESTBOOK_NAME)
+    
+    with client.context():
+        greeting = Greeting(parent=guestbook_key(guestbook_name))
+
+        user = users.get_current_user()
+        if user:
+            greeting.author = Author(
+                identity=user.user_id(),
+                email=user.email())
+
+        greeting.content = request.form.get('content')
+        greeting.put()
+
+    return redirect('/?' + urllib.parse.urlencode({'guestbook_name': guestbook_name}))
+
+if __name__ == '__main__':
+    app.run(host='127.0.0.1', port=8080, debug=True)
diff --git a/requirements.txt b/requirements.txt
new file mode 100644
index 0000000..c9aa280
--- /dev/null
+++ b/requirements.txt
@@ -0,0 +1,4 @@
+Flask==3.0.3
+google-cloud-ndb==2.3.1
+appengine-python-standard==1.1.6
+gunicorn==23.0.0
diff --git a/index.html b/templates/index.html
similarity index 100%
rename from index.html
rename to templates/index.html