: Offers 16 levels and 30 bosses. It is widely available on legacy indie game hosting sites like Uptodown .
: An expanded "ultimate" version with 21 levels, 35 bosses, a 60+ track soundtrack, and local co-op. Super Hydorah on Steam Super Hydorah Free Download
If you are specifically looking for a free experience, the developer originally released the base version, Hydorah , as a freeware title. : Offers 16 levels and 30 bosses