Vitepress

// .vitepress/theme/index.ts
import DefaultTheme from 'vitepress/theme'
import './custom.css'

export default DefaultTheme

/* .vitepress/theme/custom.css */
:root {
  /* Brand colors */
  --vp-c-brand-1: #646cff;
  --vp-c-brand-2: #747bff;
  --vp-c-brand-3: #9499ff;
  
  /* Backgrounds */
  --vp-c-bg: #ffffff;
  --vp-c-bg-soft: #f6f6f7;
  
  /* Text */
  --vp-c-text-1: #213547;
  --vp-c-text-2: #476582;
}

.dark {
  --vp-c-brand-1: #747bff;
  --vp-c-bg: #1a1a1a;
}

:root {
  --vp-nav-height: 4rem;
  --vp-nav-bg-color: color-mix(in srgb, var(--vp-c-bg) 65%, transparent);
  --vp-nav-home-bg-color: transparent; /* while unscrolled on the home page */
  --vp-nav-backdrop-filter: saturate(180%) blur(8px);
  --vp-nav-divider-color: var(--vp-c-gutter);
  --vp-nav-screen-bg-color: var(--vp-c-bg);
}

:root {
  /* Gradient name color */
  --vp-home-hero-name-color: transparent;
  --vp-home-hero-name-background: linear-gradient(120deg, #bd34fe, #41d1ff);
  
  /* Hero image glow */
  --vp-home-hero-image-background-image: linear-gradient(-45deg, #bd34fe 50%, #47caff 50%);
  --vp-home-hero-image-filter: blur(44px);
}

// .vitepress/theme/index.ts
import DefaultTheme from 'vitepress/theme-without-fonts'
import './fonts.css'

export default DefaultTheme

/* .vitepress/theme/fonts.css */
@font-face {
  font-family: 'MyFont';
  src: url('/fonts/myfont.woff2') format('woff2');
}

:root {
  --vp-font-family-base: 'MyFont', sans-serif;
  --vp-font-family-mono: 'Fira Code', monospace;
}

// .vitepress/config.ts
export default {
  transformHead({ assets }) {
    const fontFile = assets.find(file => /myfont\.[\w-]+\.woff2/.test(file))
    if (fontFile) {
      return [
        ['link', { rel: 'preload', href: fontFile, as: 'font', type: 'font/woff2', crossorigin: '' }]
      ]
    }
  }
}

// .vitepress/theme/index.ts
import DefaultTheme from 'vitepress/theme'
import MyComponent from './components/MyComponent.vue'

export default {
  extends: DefaultTheme,
  enhanceApp({ app }) {
    app.component('MyComponent', MyComponent)
  }
}

<MyComponent :prop="value" />

// .vitepress/theme/index.ts
import DefaultTheme from 'vitepress/theme'
import MyLayout from './MyLayout.vue'

export default {
  extends: DefaultTheme,
  Layout: MyLayout
}

<!-- .vitepress/theme/MyLayout.vue -->
<script setup>
import DefaultTheme from 'vitepress/theme'
const { Layout } = DefaultTheme
</script>

<template>
  <Layout>
    <template #aside-outline-before>
      <div>Above outline</div>
    </template>
    
    <template #doc-before>
      <div>Before doc content</div>
    </template>
    
    <template #doc-after>
      <div>After doc content</div>
    </template>
  </Layout>
</template>

// .vitepress/theme/index.ts
import { h } from 'vue'
import DefaultTheme from 'vitepress/theme'
import MyComponent from './MyComponent.vue'

export default {
  extends: DefaultTheme,
  Layout() {
    return h(DefaultTheme.Layout, null, {
      'aside-outline-before': () => h(MyComponent)
    })
  }
}

// .vitepress/config.ts
import { fileURLToPath, URL } from 'node:url'

export default {
  vite: {
    resolve: {
      alias: [
        {
          find: /^.*\/VPNavBar\.vue$/,
          replacement: fileURLToPath(
            new URL('./theme/components/CustomNavBar.vue', import.meta.url)
          )
        }
      ]
    }
  }
}

<!-- .vitepress/theme/Layout.vue -->
<script setup>
import { useData } from 'vitepress'
import DefaultTheme from 'vitepress/theme'
import { nextTick, provide } from 'vue'

const { isDark } = useData()

provide('toggle-appearance', async ({ clientX: x, clientY: y }) => {
  if (!document.startViewTransition) {
    isDark.value = !isDark.value
    return
  }

  const clipPath = [
    `circle(0px at ${x}px ${y}px)`,
    `circle(${Math.hypot(Math.max(x, innerWidth - x), Math.max(y, innerHeight - y))}px at ${x}px ${y}px)`
  ]

  await document.startViewTransition(async () => {
    isDark.value = !isDark.value
    await nextTick()
  }).ready

  document.documentElement.animate(
    { clipPath: isDark.value ? clipPath.reverse() : clipPath },
    { duration: 300, easing: 'ease-in', pseudoElement: `::view-transition-${isDark.value ? 'old' : 'new'}(root)` }
  )
})
</script>

<template>
  <DefaultTheme.Layout />
</template>

<VPIcon icon="lucide:rocket" />

<script setup>
import { useIcon } from 'vitepress'
import { useTemplateRef } from 'vue'

const el = useTemplateRef('el')
const iconClass = useIcon('lucide:rocket', el)
</script>

<template><span ref="el" :class="iconClass" /></template>

// .vitepress/theme/index.ts
import { watch } from 'vue'
import { useData } from 'vitepress'
import DefaultTheme from 'vitepress/theme'

export default {
  extends: DefaultTheme,
  enhanceApp({ router }) {
    router.onBeforeRouteChange = (to) => { /* return false to cancel */ }
    router.onAfterRouteChange = (to) => console.log('navigated to', to)
  },
  setup() {
    const { page } = useData()
    watch(() => page.value.relativePath, (p) => console.log('now viewing', p))
  }
}