Options -Indexes
RewriteEngine On

# Route all /api/* requests to api.php
RewriteCond %{REQUEST_URI} ^/api(/|$)
RewriteRule ^api(/.*)?$ api.php [QSA,L]

# Everything else serves static files or index.html
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.html [L]