All assets are public domain (CC0)

See: https://opengameart.org/art-search-advanced?keys=space&title=&field_art_tags_tid_op=or&field_art_tags_tid=&name=&field_art_type_tid%5B%5D=9&field_art_type_tid%5B%5D=10&field_art_type_tid%5B%5D=7273&field_art_type_tid%5B%5D=14&field_art_type_tid%5B%5D=12&field_art_type_tid%5B%5D=13&field_art_type_tid%5B%5D=11&field_art_licenses_tid%5B%5D=4&sort_by=score&sort_order=DESC&items_per_page=24&Collection=

Credits:

Asteroid images: BlackMoon Design
Background image: Cuzco
Background sound: Aquinn
Explosion sounds: Kenney (Kenney.nl)
Ship explosion sound: Bart
Shot sounds: Kenney (Kenney.nl)
Shot images: Bonsaiheldin
Ship images: Kenny (Kenney.nl)
Vanish sound: Krial