diff --git a/README.md b/README.md
index 74d2829..19d295e 100644
--- a/README.md
+++ b/README.md
@@ -4,23 +4,28 @@ Embed a mastodon feed in your blog et cetera.
 
 Preview (note: domain name incoming): https://mastofeed.herokuapp.com/
 
-## Usage guide
+## User guide
 
 The homepage has a tool for generating iframe code for you, with a sensible `sandbox` attribute.  The feeds fit comfortably in a 400px wide area.
 
 ## API
 
-### GET `/api/feed?url=${url}`
+### GET `/api/feed`
 
-> example: `/api/feed/url=https%3A%2F%2Foctodon.social%2Fusers%2Ffenwick67.atom`
+> example: `/api/feed?url=https%3A%2F%2Foctodon.social%2Fusers%2Ffenwick67.atom&scale=90&theme=light`
 
 Returns a html page which displays a mastodon feed for an atom feed URL.  Note that URLs must be URI encoded (i.e. `encodeURIComponent('https://octodon.social/users/fenwick67.atom')` ).
 
-Mastodon Atom feed URLs follow this convention:
+Querystring options:
 
-`https://${instance}/users/${username}.atom`
 
-## Installation
+| option | required | description |
+| ------ | -------- | ----------- |
+| `url` | **yes** | Mastodon Atom feed URL |
+| `style` | no | either `dark` or `light`, to select the UI theme (default is `dark`). |
+| `size` | no | the scale of the UI in percent. |
+
+## Server Installation
 
 This is a straightforward node project with zero databases or anything, you should just be able to run `npm install` and then `npm start` to get up and running.  Set your `PORT` environment variable to change the port it listens on.