Area 1 (US: Round 16)[edit]
This area contains twenty-four Large Invaders, twenty-eight Medium Invaders and ten Small Invaders in two separate horizontally-moving formations; the song you'll be hearing from the Yamaha YM-2610 is identical to that for World 2A.
Area 2 (US: Round 17)[edit]
This area (again) contains twenty-two Large Invaders, twenty-two Medium Invaders, and eleven Small Invaders in a horizontally-moving formation; however, some of the invaders shall break away from it and fly around directly above the two CG30s, while firing bullets down at them from there and screeching metallically from the Yamaha YM-2610.
Area 3 (US: Round 18)[edit]
This area, like the previous one, contains twenty-two Large Invaders, twenty-two Medium Invaders, and eleven Small Invaders in a horizontally-moving formation; but this time, when one is killed, the remainder of its column drops down to the bottom of the formation. Once you clear it, the "boss" theme will begin to be heard from the Yamaha YM-2610.
Area 4 (US: Round 19)[edit]
As the (third, if you are playing the US version) Boss Invader comes down into view, from the top of the screen, it shall fire six missiles down at the two CG30s from its sides; the eye (which is actually a shuriken) is its only vulnerable point and it will occasionally drop it before it returns to it like a boomerang. Once you have hit the shuriken forty-five times, it will explode and fall off the bottom of the screen, and the player who registered the killer shot will (once again, if you're playing the US version) receive 50000 points - and the game will then return to the zone selection screen, and you will have ten seconds to choose between World 3C and World 3D (but if you're playing the US version, you will proceed to World 3A or "Round 20", the theme for which is that remix of the first two "SI" games' main themes heard in World 1A).