diff --git a/components/__tests__/theme-provider.test.tsx b/components/__tests__/theme-provider.test.tsx
new file mode 100644
index 0000000..6a6625a
--- /dev/null
+++ b/components/__tests__/theme-provider.test.tsx
@@ -0,0 +1,51 @@
+import React from 'react'
+import { render, waitFor, cleanup } from '@testing-library/react'
+
+jest.mock('next-themes', () => {
+  return {
+    __esModule: true,
+    ThemeProvider: ({ children }: any) => <div>{children}</div>,
+    useTheme: jest.fn(),
+  }
+})
+
+import { ThemeProvider } from '../theme-provider'
+import { useTheme } from 'next-themes'
+
+afterEach(() => {
+  cleanup()
+  // remove any css vars we set
+  ;['bg', 'text', 'muted', 'accent'].forEach((k) =>
+    document.documentElement.style.removeProperty(`--${k}`),
+  )
+})
+
+test('applies dark CSS custom properties when theme is dark', async () => {
+  ;(useTheme as jest.Mock).mockReturnValue({ resolvedTheme: 'dark' })
+
+  render(
+    <ThemeProvider>
+      <div>child</div>
+    </ThemeProvider>,
+  )
+
+  await waitFor(() => {
+    expect(getComputedStyle(document.documentElement).getPropertyValue('--bg').trim()).toBe('#0b1220')
+    expect(getComputedStyle(document.documentElement).getPropertyValue('--text').trim()).toBe('#e6eef8')
+  })
+})
+
+test('applies light CSS custom properties when theme is light', async () => {
+  ;(useTheme as jest.Mock).mockReturnValue({ resolvedTheme: 'light' })
+
+  render(
+    <ThemeProvider>
+      <div>child</div>
+    </ThemeProvider>,
+  )
+
+  await waitFor(() => {
+    expect(getComputedStyle(document.documentElement).getPropertyValue('--bg').trim()).toBe('#ffffff')
+    expect(getComputedStyle(document.documentElement).getPropertyValue('--text').trim()).toBe('#0b1220')
+  })
+})
diff --git a/components/theme-provider.tsx b/components/theme-provider.tsx
index bf85d22..b9a0d51 100644
--- a/components/theme-provider.tsx
+++ b/components/theme-provider.tsx
@@ -1,8 +1,48 @@
 'use client'
 
 import * as React from 'react'
-import { ThemeProvider as NextThemesProvider, type ThemeProviderProps } from 'next-themes'
+import {
+  ThemeProvider as NextThemesProvider,
+  useTheme,
+  type ThemeProviderProps,
+} from 'next-themes'
+
+const ROOT_CSS_VARS: Record<string, { light: string; dark: string }> = {
+  'bg': { light: '#ffffff', dark: '#0b1220' },
+  'text': { light: '#0b1220', dark: '#e6eef8' },
+  'muted': { light: '#6b7280', dark: '#9aa4b2' },
+  'accent': { light: '#0ea5e9', dark: '#38bdf8' },
+}
+
+function ThemeCustomProps() {
+  const { resolvedTheme } = useTheme() as { resolvedTheme?: string }
+
+  React.useEffect(() => {
+    const theme = resolvedTheme ?? 'light'
+    Object.entries(ROOT_CSS_VARS).forEach(([name, val]) => {
+      const value = theme === 'dark' ? val.dark : val.light
+      try {
+        document.documentElement.style.setProperty(`--${name}`, value)
+      } catch (e) {
+        // ignore in non-DOM environments
+      }
+    })
+  }, [resolvedTheme])
+
+  return null
+}
 
 export function ThemeProvider({ children, ...props }: ThemeProviderProps) {
-  return <NextThemesProvider {...props}>{children}</NextThemesProvider>
+  return (
+    <NextThemesProvider
+      {...props}
+      attribute="class"
+      enableSystem
+      defaultTheme="system"
+      storageKey="theme"
+    >
+      <ThemeCustomProps />
+      {children}
+    </NextThemesProvider>
+  )
 }