Alpha Mission II / ASO II - Last Guardian (prototype) [Prototype]

This is a prototype build of Alpha Mission II, also known as ASO II: Last Guardian, a vertical-scrolling shoot 'em up originally developed for the Neo Geo home arcade system by SNK. Prototypes like this one offer a rare look at the game's development process, sometimes with unfinished graphics, placeholder text, or different balancing compared to the final retail version. If you have played the commercial release, this variant may feel familiar yet slightly off, which is part of the appeal for preservation fans.

The core gameplay puts you in control of a fighter ship navigating vertically scrolling stages filled with enemy formations and bullets. You can pick up weapon power-ups to upgrade your main shot, and the special feature here is the "Conqueror" system: by shooting down certain enemies, you can capture them and turn them into support fighters that fly alongside you or attack independently. The goal is to survive each stage and defeat the end boss, using a combination of reflexes, pattern recognition, and smart use of your captured allies. As a prototype, some of these mechanics might behave differently than in the final version.

For retro enthusiasts, this prototype is a historical artifact that helps document how a classic Neo Geo shooter evolved before hitting arcades. It is not a major departure from the familiar Alpha Mission II experience, but it gives insight into SNK's development and testing process. If you have played the final game, you might notice oddities in enemy placement, weapon behavior, or even missing sound effects. It is a niche treat rather than a polished standalone game, but well worth a look for anyone curious about the inner workings of 1990s arcade development.