server {
    listen 80;
    server_name localhost;
    root /usr/share/nginx/html;
    index index.html;

    # Security headers (Stage 2B §24.3)
    add_header X-Content-Type-Options "nosniff" always;
    add_header X-Frame-Options "DENY" always;
    add_header Referrer-Policy "strict-origin-when-cross-origin" always;
    add_header Permissions-Policy "camera=(), microphone=(), geolocation=()" always;

    # gzip for text payloads (GLB/STL are already compressed/binary)
    gzip on;
    gzip_vary on;
    gzip_min_length 1024;
    gzip_comp_level 6;
    gzip_types text/plain text/css application/json application/javascript image/svg+xml;

    # Explicit 3D model MIME types
    types {
        model/gltf-binary glb;
        model/stl stl;
    }

    location = /version.json {
        add_header Cache-Control "no-store, no-cache, must-revalidate";
        add_header X-Content-Type-Options "nosniff" always;
        try_files $uri =404;
    }

    location / {
        try_files $uri $uri/ /index.html;
    }

    location /assets/ {
        expires 1y;
        add_header Cache-Control "public, immutable";
    }

    location /models/ {
        expires 1y;
        add_header Cache-Control "public, immutable";
    }

    location /draco/ {
        expires 1y;
        add_header Cache-Control "public, immutable";
    }
}