## Philosophy
Minimal PHP for modern conveniences. Prioritize longevity (decade-scale maintainability) by avoiding volatile dependencies. Strictly add only what's essential—readable, simple, and future-proof.

## Core Constraints
**Minimalism:** Only essential tech (HTML, PHP 8.4+, CSS). No JS, frameworks, build tools, or package managers. Comments only for major sections.

**Frontend:**
- Classless, semantic HTML5
- Modern CSS: nesting, `oklch()`, grid, `clamp()`, logical props
- Responsive via fluid typography + flexible layouts

**Security:**
- Path validation blocks traversal
- Files restricted to document root
- Strict MIME types + no direct user-input execution

## Code Style
**PHP:** Modern syntax (arrow functions, null coalescing, match). Type hints where practical. Ternary for simple conditionals. Single-purpose functions.

**CSS:** Variables, native nesting, grid layouts. `clamp()` over `@media`. Relative units > pixels.

**Templates:** Escape output (`htmlspecialchars()` for UGC). Short echo tags (`<?= $var ?>`).