The theme is similar to Choplifter in that you must rescue hostages and bomb ground-based enemies. It has the caverns of Scramble and the movement and firing of Defender. This combination works as well as mixing ice cream with salt. You begin on an upper level of the sky, where you encounter some aliens. Descend a little further and you'll find Scramble-esque cave passages, where you're supposed to find and rescue the hostages. Down there you're opposed by a number of adversaries -- enemy choppers and missile launchers -- which are also present on the top level.
The problem lies in the viewing area of the screen. Unlike other games of its ilk, you cannot see the entire playfield from top to bottom, making for some awkward situations. And the screen doesn't scroll up or down as you move, either. As you reach the bottom portion of the top level, you're suddenly at the top of the lower level, where you might be right in the line of fire by the missile launchers. It's terribly awkward to say the least. And even though there's a Defender-like radar screen to help you knowing where your enemies are located, it still doesn't help much. You could very well be in the top level but missiles from enemies in the lower levels can still sneak up from below and demolish you. Not exactly fair, is it? To make matters worse, your fire is about as powerful as a squirt gun. You have to hit everything just right in order to destroy it, and sometimes the enemy simply refuses to be killed. Finally, the walls become invisible on the second level. Huh? You've got to be a bigtime masochist to enjoy playing a game where you blow up after running into something that you can't even see.