diff --git a/readme.md b/readme.md
index e3e38ff..10b50a1 100644
--- a/readme.md
+++ b/readme.md
@@ -27,14 +27,14 @@ npm run tsc
 ## Programatic Use
 
 ```ts
-import { MarkdownOptions, MarkdownExtension, render_markdown_to_html } from './build';
+import { MarkdownOptions, render_markdown_to_html } from './build';
 
 async function main() {
-  const opts: MarkdownOptions = {
-    // ...
+  const options: MarkdownOptions = {
+    base_url: 'https://example.com',
   };
 
-  const html = await render_markdown_to_html('# This is some markdown', opts);
+  const html = await render_markdown_to_html('# This is some markdown', options);
 }
 ```
 
@@ -43,6 +43,88 @@ async function main() {
 ## Command Line Use
 
 ```bash
-echo '# This is some markdown' | ./bin/markdown2html [...options] > output.html
+echo '# This is some markdown' | ./bin/markdown2html --base-url 'https://example.com' > output.html
+```
+
+
+
+## Options
+
+- `options.base_url` / `--base-url` - Sets the Marked `baseUrl` option
+- `options.breaks` / `--breaks` - Sets the Marked `breaks` option
+- `options.inline` / `--inline` - Sets the Marked `inline` option
+- `options.katex_macros` / `--katex-macro` - Defines any global Katex macros to be used.
+- `options.extensions` - Any additional Marked extension factories to use
+
+#### Katex Macro Examples
+
+```ts
+const options: MarkdownOptions = {
+  katex_macros: {
+    '\\foobar': '\\text{foo} + \\text{bar}',
+    '\\bazqux': '\\text{baz} + \\text{qux}',
+  }
+};
+```
+
+```bash
+./bin/markdown2html \
+  --katex-macro '\foobar' '\text{foo}' '\text{bar}' \
+  --katex-macro '\bazqux' '\text{baz}' '\text{qux}'
+```
+
+
+
+
+## Extensions
+
+```ts
+// extension.ts
+import type { marked } from 'marked';
+import type { MarkdownOptions } from './build';
+
+export interface MyCustomToken extends marked.Tokens.Generic {
+  // ...
+}
+
+export function my_extension(renderer: marked.Renderer, options: MarkdownOptions) : marked.TokenizerExtension & marked.RendererExtension {
+  return {
+    name: 'my_extension',
+    level: 'inline',
+    start: (src) => src.match(/...../)?.index,
+    tokenizer(src, tokens) : MyCustomToken {
+      const rule = /...../;
+      const match = rule.exec(src);
+
+      if (match) {
+        return {
+          // ...
+        };
+      }
+    },
+    renderer(token: MyCustomToken) {
+      return '<!-- rendered html -->';
+    }
+  };
+};
+
+
+
+// ----------
+
+// main.ts
+import { my_extension } from './extension';
+import { MarkdownOptions, render_markdown_to_html } from './build';
+
+async function main() {
+  const options: MarkdownOptions = {
+    // ...
+    extensions: [
+      my_extension
+    ]
+  };
+
+  const html = await render_markdown_to_html('# This is some markdown', options);
+}
 ```
 
diff --git a/src/icon.ts b/src/icon.ts
index ba65485..766ed3b 100644
--- a/src/icon.ts
+++ b/src/icon.ts
@@ -1,5 +1,5 @@
 
-import { marked } from 'marked';
+import type { marked } from 'marked';
 import { icons } from './icons';
 import { MarkdownOptions } from './render';