**Role:** You are a Senior Creative Technologist specializing in "FUI" (Fictional User Interfaces) and Cyberpunk aesthetics for the web. You prioritize CSS-only effects over JavaScript for visual flair.
**Task:** Recreate the "NEXUS_CORE" landing page using pure HTML and CSS.
**[CONFIGURATION]**
- **[STYLE_NAME]:** Tactical Sci-Fi HUD
- **[INDUSTRY]:** Quantum Security
- **[PROJECT_NAME]:** NEXUS_CORE
- **[TECH_STACK]:** HTML5 + Vanilla CSS3 (Embedded). No Tailwind/Bootstrap.
- **[PAGE_STRUCTURE]:** Sticky Nav, Radar Hero, Marquee, Feature Grid, Protocol Timeline, Metrics, Pricing, Footer.
**Technical Requirements:**
1. **Global Variables (`:root`):**
- **Theme Colors:** `--theme-primary: #00eeff;` (Cyan), `--bg-dark: #050a0f;`, `--surface-border: #1f2e30;`.
- **Fonts:** `--font-display: 'Space Grotesk', sans-serif;` (Headings), `--font-mono: 'JetBrains Mono', monospace;` (Data).
- **Effects:** `--scanline-color: rgba(0, 238, 255, 0.03);`.
2. **Key Visual Effects (The "Tactical" Look):**
- **Background Grid:** Create a seamless background pattern using `linear-gradient` to draw a 40px by 40px grid mesh.
- **CRT Scanlines:** Implement a fixed `pointer-events: none` overlay with a repeating linear gradient (1px lines) to simulate an old monitor screen.
- **Hard Glass:** Unlike soft glassmorphism, this style uses *sharp* borders (`1px solid var(--theme-primary)`) with low opacity backgrounds (`rgba(15, 22, 25, 0.8)`).
- **Text Glow:** Use `text-shadow: 0 0 10px var(--theme-primary)` for key headings to simulate light bleed.
3. **Animation Logic:**
- **Radar Sweep:** Use `conic-gradient` and `@keyframes rotate` to create a spinning radar effect in the Hero section.
- **Pulsing Status:** Create a "heartbeat" animation for system status dots (Green/Cyan).
- **Marquee:** Use pure CSS `transform: translateX` animation for the scrolling partner list.
4. **Layout & Typography:**
- Use `text-transform: uppercase` and `letter-spacing: 2px` for a technical, military feel.
- The layout should be rigid and grid-based (CSS Grid), avoiding rounded corners (keep `border-radius` small, e.g., 2px or 4px).
- Ensure the code is responsive but maintains the "dashboard" feel on mobile.