diff --git a/README.md b/README.md
index 7137ac2..9ff85a1 100644
--- a/README.md
+++ b/README.md
@@ -111,6 +111,55 @@ console.log(<Profile pic={user.pic} bio={user.bio} />)
 console.log(<Profile size="small" pic={user.pic} bio={user.bio} />)
 ```
 
+### selectors
+
+Use `selectors` to write custom CSS selectors. Reference the current
+element with `&` and other parts with `@PartName`:
+
+```tsx
+const Checkbox = define("Checkbox", {
+  parts: {
+    Input: {
+      base: "input[type=checkbox]",
+      display: "none",
+    },
+    Label: {
+      base: "label",
+      padding: 10,
+      cursor: "pointer",
+      color: "gray",
+
+      selectors: {
+        // style Label when Input is checked
+        "@Input:checked + &": {
+          color: "green",
+          fontWeight: "bold",
+        },
+        // style Label when Input is disabled
+        "@Input:disabled + &": {
+          opacity: 0.5,
+          cursor: "not-allowed",
+        },
+      },
+    },
+  },
+
+  render({ props, parts: { Root, Input, Label } }) {
+    return (
+      <Root>
+        <Label>
+          <Input checked={props.checked} />
+          {props.label}
+        </Label>
+      </Root>
+    )
+  },
+})
+
+// Usage
+<Checkbox label="Agree to terms" checked />
+```
+
 ## themes
 
 built-in support for CSS variables with full type safety:
diff --git a/examples/profile.tsx b/examples/profile.tsx
index 68e728c..9078a08 100644
--- a/examples/profile.tsx
+++ b/examples/profile.tsx
@@ -9,8 +9,8 @@ const UserProfile = define('UserProfile', {
   maxWidth: 600,
   margin: "0 auto",
   background: theme('colors-bgElevated'),
-  border: `1px solid ${theme('colors-border')}`,
   borderRadius: theme('radius-md'),
+  border: theme('colors-accent'),
 
   parts: {
     Header: {
diff --git a/examples/spa/app.tsx b/examples/spa/app.tsx
index 465c12a..a92d035 100644
--- a/examples/spa/app.tsx
+++ b/examples/spa/app.tsx
@@ -35,16 +35,9 @@ const ThemePicker = define('SpaThemePicker', {
   },
 
   render({ parts: { Root, Select } }) {
-    const handleChange = (e: Event) => {
-      const target = e.target as HTMLSelectElement
-      const themeName = target.value
-      document.body.setAttribute('data-theme', themeName)
-      localStorage.setItem('theme', themeName)
-    }
-
     return (
       <Root>
-        <Select id="theme-select" onchange={handleChange}>
+        <Select id="theme-select" onChange={themeChanged}>
           <option value="dark">Dark</option>
           <option value="light">Light</option>
         </Select>
@@ -53,6 +46,13 @@ const ThemePicker = define('SpaThemePicker', {
   }
 })
 
+function themeChanged(e: Event) {
+  const target = e.target as HTMLSelectElement
+  const themeName = target.value
+  document.body.setAttribute('data-theme', themeName)
+  localStorage.setItem('theme', themeName)
+}
+
 export const Main = define('SpaMain', {
   base: 'div',
 
diff --git a/src/index.tsx b/src/index.tsx
index 45cf5ee..db2c583 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -51,13 +51,12 @@ export function createThemedVar<T extends Record<string, any>>(_themes: T) {
 }
 
 // Simplified API: register multiple themes and get typed themeVar in one call
-export function createThemes<
-  T extends Record<string, Record<string, string | number>>
->(themes: T) {
-  const registeredThemes: Record<string, Record<string, string>> = {}
+type Theme = Record<string, string | number>
+export function createThemes<T extends Record<string, Theme>>(themes: T) {
+  const registeredThemes = {} as T
 
   for (const [name, values] of Object.entries(themes)) {
-    registeredThemes[name] = createTheme(name, values)
+    (registeredThemes as any)[name] = createTheme(name, values)
   }
 
   return createThemedVar(registeredThemes)