This pack contains both the arcade classics Gradius I and II, ported to Windows 95, Sony Playstation and Sega Saturn.
Story: the Bacterians are attacking the planet Gradius, and in a state-of-the-art fighter ship you have to stop them. Both games have similar gameplay and graphics, with only different music and level layout setting them apart.
Each of these side-scrolling shooters has over a dozen levels each, all of which are completely unique. There are no enemy types that are re-used from level to level (except for the boss who is the same in every level). You can collect powerups that provide things like extra speed, laser shots, target-seeking missiles, shields, etc.
While there have been many small modernising touches made to the games, there is still no ability to save. Be prepared to set aside a considerable amount of time to finish in one go.