In the year 2034, the metallic element "Busterium" was discovered at the bottom of the Pacific Ocean by Lerman Matsunaga, a multinational corporation, and the world had greatly changed. As a result of Busterium, "Buster Engines" were created, along with the central supercomputer "Bustersystem All Controller", or BAC. However, in 2061, BAC suddenly becomes haywire and declares war on all mankind, using the Buster Engines to create various machines under its control. BAC had quickly taken over the planet, and half of the world's population was reduced. But a group within Lerman Matsunaga had learned about the dangers of BAC and Buster Engines, and created an anti-BAC weapon called the "Rolling Gun". Soon, the ship that had wielded the Rolling Gun, Anti-BAC Suppression Independent Control Armament "Rolling Gun" Deployment Warship RF-42R STORK, was rolled out. Humanity then begins "Operation Downfall", a final mission to destroy BAC once and for all. But things won't be easy, as BAC had already taken over Lerman Matsunaga as its fortress.
An upcoming patch, Over Power, was soon announced. In addition to making the game slightly harder, there will also be a new bullet canceling mechanic, as well as an arranged soundtrack.
Rolling Gunner provides example of:
- Anti-Frustration Features: Getting hit with bombs in stock will trigger an auto-bomb to avoid letting your bombs go to waste. As a compromise however, this also uses up all your bombs instead of just one.
- Arrange Mode: Over Power allows you to independently aim your drone's shots with the right analog stick, and the drone now absorbs bullets a la R-Type. Instead of bombs, you get a slowly-regenerating shield meter and getting hit will take off shield instead of destroying you, so long as you have at least one whole shield segment, and you gain capacity upgrades to your shield bar on stages 3 and 5. It is considerably easier than the base game, being more focused on scoring than survival. While this mode can be played without using the right analog stick (e.g. with an arcade stick or a 2D-focused gamepad without analog sticks), it is considerably less functional that way, as you can't independently aim your option and the rapid shot button is replaced with the Fighter/Gunner change button, but the shot button still behaves like it does in the base game, firing in Fighter Mode if tapped and in Gunner mode if held down.
- Boss Subtitles:
- YB-12 Prototype Battle Bomber "Goose".
- Urban Buster Reactor Plant "BP-103".
- R-45 Huge Battle Device "Penetrator".
- CF-7 Cruise Chaser "Pterodactylus".
- Battle Attack Satellite "Fire Dragon No. 3".
- Mobile Fortress "BAC".
- Averted with the True Final Boss, which is labeled as "BAC Core".
- Bullet Hell: Even on Casual Mode, there's still a lot of bullets fired at you. Especially when you face the True Final Boss. This gets taken Up to Eleven on Expert Mode.
- Expy: BAC's core resembles the Stone-Like from Radiant Silvergun and Ikaruga.
- The Rolling Gun itself, with its white body, red highlights with a little blue, looks a little like G1 Starscream.
- Humongous Mecha: The Mission 3 boss, Penetrator, and BAC's first form.
- Kill Sat: The Mission 5 boss, Fire Dragon No. 3.
- Mega-Corp: Lerman Matsunaga.
- Nintendo Hard: This is a Bullet Hell game, after all.
- No-Sell: Use a bomb on BAC's final form, it will shield itself with a barrier, similar to Hibachi.
- True Final Boss: BAC's One-Winged Angel form can only be fought if you defeated BAC's first form without using a continue and stayed on Rank 15. On Casual and Novice Modes, you can simply reach it without continuing. But on Original and Expert Modes, you have to be on Rank 15. Over Power doubles the rank requirement to Rank 30.
- Villain: Exit, Stage Left: Once you catch up to BAC in Mission 4, it escapes to the moon on a rocket, forcing you to pursue it in space.