复古未来主义

Build a full-screen hero landing page for a creative agency called "Mainframe" using React, TypeScript, Vite, and Tailwind CSS. Here is every detail:

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FONTS

Load two fonts in `index.html` via these stylesheet links:
- Heading: `https://db.onlinewebfonts.com/c/5ac3fe7c6abd2f62067f266d89671492?family=HelveticaNowDisplay-Medium`
- Body: `https://db.onlinewebfonts.com/c/1aa3377e489837a26d019bba501e779d?family=HelveticaNowDisplayW01-Rg`

In `index.css`, define CSS variables:
```css
:root {
  --font-heading: 'HelveticaNowDisplay-Medium', 'Helvetica Neue', Arial, sans-serif;
  --font-body: 'HelveticaNowDisplayW01-Rg', 'Helvetica Neue', Arial, sans-serif;
}
body {
  font-family: var(--font-body);
}
```

The entire page uses `var(--font-body)` except the logo text which uses `var(--font-heading)`.

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BACKGROUND VIDEO (mouse-scrub controlled)

- A full-screen `` element is `position: fixed; inset: 0; z-index: 0; object-fit: cover; object-position: 70% center;`.
- Video source URL: `https://d8j0ntlcm91z4.cloudfront.net/user_38xzZboKViGWJOttwIXH07lWA1P/hf_20260530_042513_df96a13b-6155-4f6e-8b93-c9dee66fba08.mp4`
- The video is `muted`, `playsInline`, `preload="auto"`. It does NOT autoplay.
- The video scrubs forward/backward based on horizontal mouse movement. Use a `mousemove` event listener on `window`. Track `prevX`, compute `delta = currentX - prevX`, convert to a time offset: `(delta / window.innerWidth)  SENSITIVITY  video.duration` where `SENSITIVITY = 0.8`. Clamp `targetTime` between 0 and `video.duration`. Use `video.currentTime` to seek, and an `onSeeked` handler to queue the next seek if `targetTime` has moved, preventing seek-flooding.

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**NAVBAR (fixed, z-index: 10)**

- Fixed to top, full width. Padding: `px-5 sm:px-8 py-4 sm:py-5`. Flex row, `justify-between`, `items-center`.
- **Logo (left):** Flex row with `gap-3`. Text "Mainframe(R)" (use the registered trademark symbol) at `text-[21px] sm:text-[26px]`, `tracking-tight`, black, using `var(--font-heading)`. Beside it, a decorative asterisk character `✳︎` at `text-[25px] sm:text-[30px]`, black, `select-none`, `letter-spacing: -0.02em`.
- **Desktop nav links (center, hidden below md):** Flex row, `text-[23px]`, black. Links: "Labs", "Studio", "Openings", "Shop" separated by commas rendered as `, `. Each link has `hover:opacity-60 transition-opacity`.
- **Desktop CTA (right, hidden below md):** An anchor "Get in touch" at `text-[23px]`, black, `underline underline-offset-2`, `hover:opacity-60 transition-opacity`.
- **Mobile hamburger (visible below md):** A button with 3 horizontal bars (each `w-6 h-[2px] bg-black`), spaced with `gap-[5px]`. On toggle, the top bar rotates 45deg and translates down 7px, middle bar fades to opacity 0, bottom bar rotates -45deg and translates up 7px. All transitions are `duration-300`.
- **Mobile overlay (z-index: 9):** `fixed inset-0 bg-white/95 backdrop-blur-sm`, flex column, vertically centered, left-aligned with `px-8 gap-8`. Same links at `text-[32px] font-medium`, plus "Get in touch" underlined. Fades in/out with `opacity` and `pointerEvents` toggled. Hidden on md+.

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**HERO SECTION (z-index: 1)**

- Full `h-screen`, flex column. On mobile: `justify-end pb-12`. On `md:`: `justify-center pb-0`. Horizontal padding: `px-5 sm:px-8 md:px-10`. `overflow-hidden`.
- Content container: `max-w-xl`, `relative z-10`.

**1. Blurred intro label:**
- `pointer-events-none`, `select-none`, `mb-5 sm:mb-6`.
- Font size: `clamp(18px, 4vw, 26px)`, `line-height: 1.3`, `font-weight: 400`, `color: #000`, `filter: blur(4px)`.
- Two lines of text:
  - Line 1: "Hey there, meet A.R.I.A,"
  - Line 2: "Mainframe's Adaptive Response Interface Agent"
- Separated by a `
`.

**2. Typewriter text:**
- Text: `"Glad you stopped in. Good taste tends to find us. Now, what are we building?"`
- Custom `useTypewriter` hook: takes `text`, `speed` (default 38ms per character), `startDelay` (default 600ms). After the delay, an interval reveals one character at a time. Returns `{ displayed, done }`.
- Rendered in a `

` tag, black, `mb-5 sm:mb-6`, font size `clamp(18px, 4vw, 26px)`, `line-height: 1.35`, `font-weight: 400`, `min-height: 54px`.
- While typing, show a blinking cursor: `inline-block w-[2px] h-[1.1em] bg-black align-middle ml-[2px]` with CSS animation `blink 1s step-end infinite` (`opacity: 1 at 0%/100%, 0 at 50%`). Cursor disappears when `done` is true.

**3. Action pill buttons:**
- Appear with a fade-in + slide-up animation (`opacity 0->1`, `translateY(8px)->0`, `transition: opacity 0.4s ease, transform 0.4s ease`). They become visible 400ms after page load, independent of the typewriter animation (do NOT wait for typing to finish).
- Container: `flex flex-wrap gap-y-1`.
- **4 white pill buttons:** Labels: "Pitch us an idea", "Come work here", "Send a brief hello", "See how we operate". Each is `inline-flex items-center justify-center bg-white text-black border border-black/10 rounded-full text-[13px] sm:text-[15px] px-4 sm:px-5 py-[0.3em] mx-[0.2em] mb-[0.4em] white-space: nowrap`. Hover: `bg-black text-white`, `transition-colors duration-200`.
- **1 outline pill button:** Text "Reach us: [已省略邮箱]" (email is underlined with `underline-offset-1`), followed by a small 12x12 copy icon (inline SVG of two overlapping rectangles). Styled: `text-white bg-transparent border border-white rounded-full`, same sizing as above, with `gap-2 sm:gap-3` between text and icon. Hover: `bg-white text-black`. On click, copies "[已省略邮箱]" to clipboard via `navigator.clipboard.writeText()`.

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DEPENDENCIES

Only React, ReactDOM, Tailwind CSS, and Vite. No other UI libraries. Lucide-react is available but not used in this component.