RewriteEngine On

# ----------------------------------------
# 1) Root → router.php
# ----------------------------------------
RewriteRule ^$ router.php [L]

# ----------------------------------------
# 2) Allow existing files
# ----------------------------------------
RewriteCond %{REQUEST_FILENAME} -f
RewriteRule ^ - [L]

# ----------------------------------------
# 3) Allow existing directories
# ----------------------------------------
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]

# ----------------------------------------
# 4) Everything else → router.php
# ----------------------------------------
RewriteRule ^ router.php [QSA,L]