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

    gzip on;
    gzip_types text/css application/javascript application/json image/svg+xml;
    gzip_min_length 1024;

    # Hashed build assets are immutable — cache hard.
    location /assets/ {
        expires 1y;
        add_header Cache-Control "public, immutable";
        try_files $uri =404;
    }

    # Never cache the HTML shell so new deploys are picked up.
    location = /index.html {
        add_header Cache-Control "no-cache";
    }

    # SPA fallback: path-routed deep links (e.g. /drill/R3) must serve the app.
    location / {
        try_files $uri $uri/ /index.html;
    }
}