In the shooters subgenre, there has always been the eternal dispute about horizontal versus vertical. Though in between, there have also always been those which allowed for a little more variety, some scrolling in two different directions., while essentially falling into the horizontally scrolling category, connects its screens in not 100% straightforward ways, building a small river maze in the process.
The objective being the destruction of four enemy bases yet to be located. The way to victory is therefore not just to shoot faster than the rest, but also to optimize the path to take. Since the river banks are all fortified with enemy installations and mobile dangers such as boats and choppers come on top, such optimization is absolutely essential.
Though it takes much more than that, and quite frankly, more than can be reasonably expected of a player. Maneuvering the rather large boat sprite through the rather narrow river area takes a lot of effective squeezing room away, limits the degree of freedom usually used in a shooter to avoid shots and other obstacles. Although different weapons are available to get rid of particularly nasty enemies (such as targeting missiles against those flying pests), their use is rather awkward and hard to get right in the heat of the moment.
The limited animation doesn't help. Sprites are just choppily moved across the screen, variants of different perspectives being exchanged to create the illusion of the tilted, three-dimensional perspective. Nothing comes together to form a coherent overall visual impression.
With a whole three failure conditions looming over the player's head (apart from being destroyed: running out of fuel or the engine overheating), it's an impossible task. The amount of skill required to master this game is already unreasonably high, though even that is not nearly sufficient. A disproportionate amount of luck has to come on top. This, however, takes all the sense of achievement out of the rare occasions when the player actually manages to destroy one of the bases. When it's obvious it was just luck, it's simply not satisfying.