Coincidence or not, Gyruss fits a reductionist description of Galaga projected in pseudo-3D, with the playfield viewed from below, the "top" of it appearing to stretch far into the distance of deep space, and the plane of action folded around into a cylinder. The aspects lifted from Galaga are numerous; enemy ships gradually enter the playfield in sweeping formations, and those which you don't shoot down on their first pass hang back in a slightly pulsating phalanx formation until they've all entered, and then they attack. A special target can be shot to give you a double-firepower upgrade (and unlike Galaga there is no downside and it is crucial that you collect this as soon as possible). There are even "chance stages" that serve as exact analogs to Galaga's "challenging stages," with 40 enemies worth of formations harmlessly moving across the screen in predetermined patterns. If Galaga's flat playing field had simply wrapped itself around from left to right and the alien's attack patterns altered to utilize this, it would play largely the same as Gyruss, and perhaps better as some shooting precision is lost in the faked projection.
But there's something to be said for presentation, and Gyruss' 3D perspective, illusory hyperspace-motion starfield, its stereophonic soundtrack, an electronic-rock interpretation of Bach's Toccata and Fugue that might be the earliest example of in-game music that I've enjoyed listening to, do a lot to make Gyruss feel fast paced, exciting, and fun.
The "tube shooter" format invites comparisons to Atari's Tempest, but I find that in practice the games have little in common.
One addition I appreciated here is the stage progression, where you're warping from Neptune to Uranus and eventually all the way to Earth. Stages aren't hugely distinct from one another - you'll have seen every basic enemy type in the game by the time you reach Neptune, and later rounds just add different colors, attack patterns, and more aggressive AI, but it still lends a feel of desperately racing across the solar system toward home before it's too late, and that sense of progress toward a goal is something completely lacking in Galaga where the stage numbers simply go up to no real end point until you lose your last ship.
Gyruss does seem to be easier than Galaga - despite the increased difficulty of hitting ships with somewhat imprecise 3D hitboxes, enemies don't fire nearly as aggressively, it's much simpler to collect double firepower and doing so won't sacrifice lives or make you easier to hit in turn, and the few obstacle types aren't a big deal. Once you reach Jupiter, though, it starts getting dramatically harder. Enemies on the way to Mars come out fast, release their shots so closely that you can't reasonably react in time, and will dive in wide, swooping arcs prone to colliding with you. At this point you're better off avoiding the initial attacks and just sniping at them in the distance.
I never quite made it to Earth, and part of the reason was that I eventually got bored of replaying the easier phases in order to reach the later ones. From checking a longplay on Youtube, nothing special happens when you do. You get another chance round, and after that it's three warps to Neptune all over again, but with continually increasing speed and difficulty.
GAB rating: Good. Gyruss might not be the deepest or most technically sound space shooter of its time, but I had a blast while it lasted, and for the cost of a quarter per play, it's a success in my book.
The international arcade game industry shrank somewhat in 1983, and although Gyruss was a success, it didn't have the same power to move units that designer Yoshiki Okamoto's previous hit Time Pilot had. Afterward, depending on the account, he was either downsized, fired, or quit after an ultimatum. But by 1984 he joined a new studio called Capcom, where over the next 20 years he directed or otherwise contributed to multiple games in some of the biggest video arcade game franchises of all time.
Gyruss itself was ported to multiple gaming systems over the next two years including the Atari 400 and Commodore 64, and perhaps most notably to the Famicom Disk System in 1988 where it received several gameplay tweaks and additions including a plot structure, boss fights, and additional weapons.