Why would anyone try to break into a heavily defended citadel? For the lashings of loot inside, of course. But you're different, you're in it for the kicks (just as well considering the low exchange rate of computer money!).
The treasure trove is protected by four multiloaded fortresses: levels one and three are vertically-scrolling, the others horizontally-scrolling. All show the ship side-on.
To help you there's the customary power-ups: collecting one gives you triple fire, a second gives you a drone. In team-play mode player two can control this. A third power-up briefly changes you into an invulnerable eagle.