R-Gray 1 and R-Gray 2 ships
Without using any continues, complete Original Mode with any ship to unlock the R-Gray 1 and R-Gray 2 ships.
submitted by fay d. away

Art gallery
Complete Special Mode with four of any ships. If you have the R-Gray ships unlocked, you can use those ships to complete Special Mode. Each time you complete the game with a different ship, you will unlock three sets of new artworks in the art gallery (up to 12 sets are unlocked in total).
submitted by fay d. away

Cheats