The Switch has become something of a treasure trove of retro goodness, with companies like Hamster and Zerodiv bringing a host of old-school classics to the eShop on a weekly basis. For shooter fans, Nintendo's console is a real goldmine, with Blazing Star, Pulstar, Strikers 1945 and Gunbird already available for download. Now, Zerodiv has taken things to the next technological level with Psikyo's Zero Gunner 2, which – instead of being a 2D blaster – uses turn-of-the-millennium 3D visuals. Originally an arcade shooter, Zero Gunner 2 was ported to the Sega Dreamcast in Japan and today copies exchange hands for astonishing sums of cash, making the incredibly modest asking price for this eShop port all the more remarkable.

eBay value aside, Zero Gunner 2 was a pretty unique shooter on Dreamcast and that has naturally translated to the Switch version. The hook is that instead of piloting a plane or space ship, you're in the cockpit of one of three helicopters, all of which are capable of turning a full 360 degrees. Hold down the Y or A button and a circular cross-hair will appear directly in front of your craft – pushing left or right on the controller makes your heli pivot around this point. That means that unlike most shooters, you're not confined to firing in one direction, and similarly, your enemies can come from all four points of the compass, too.

Getting your head around this unique control system takes a while, but you soon realise it really open things up when it comes to gameplay. You need to watch every corner of the screen to spot incoming threats as well as constantly adjust your position to control as much of the playing area as possible. It feels at times like a twin-stick shooter and you may wonder why Zerodiv didn't add such a control configuration to the game, seeing as the Switch is equipped with two analogue sticks. However, we're glad it didn't, as it would rob Zero Gunner 2 of some of its uniqueness; mastering the unorthodox control setup is all part of the challenge and once you know what you're doing it feels brilliant.

360-degree aiming aside, Zero Gunner 2 is pretty conventional elsewhere. Your craft has a standard shot which can be powered-up by collecting 'P' items; these are dropped by red enemies and can be 'sucked' towards you ship by lifting your finger off the trigger briefly (an act which naturally means you're leaving yourself open to incoming attacks). You also have a special 'option' weapon which is best saved for the many boss encounters in the game; this can be topped up by collecting 'E' items, which are more common than 'P' power-ups. The catch is that you have to pick up a massive amount of them to gain another special weapon.

The seven levels in Zero Gunner 2 cover a wide range of locations, including an oil rig, submerged city and railroad. The stages aren't all that long but they're quite challenging, especially the later ones; bullets fly in all directions and the fact that death can come from behind as well as in front keeps you on your toes. On the plus side you can collide and actually damage smaller enemies with your rotor blades and it's also possible to shoot down certain projectiles, but the game still presents a pretty stern task – and that's on the default 'Normal' difficulty level. You can, if you so wish, drop it down for an easier ride or bump it up for a sadistic test of your reactions. It's also possible to tinker with the number of lives you have per continue, the number of continues available before it's game over and your stock of special 'option' attacks. We'd recommend you avoid doing this however, and focus on beating the game with the default settings.

Perhaps the biggest highlight of each stage is the end-of-level boss, which first takes the form of a vehicle before transforming into a fearsome mech halfway through the battle. Psikyo's previous games feature similar morphing enemies, but here they're presented in 3D and are true marvels of polygon engineering. A highlight is a submarine that fires missiles at you initially but then turns into a four-armed monster which climbs up between two submerged tower blocks to continue the fight. There's some fantastic mechanical design on display and despite the passage of time, Zero Gunner 2 still looks great. Sure, some effects are a little lame – the water splashes which accompany the submarine boss' initial appearance look more like clouds – but this is a game from 2001 after all. To its credit, Zerodiv has boosted the resolution and improved the textures so everything looks a lot sharper than it did before. If for some reason you want the game to look exactly as it did on your Japanese Dreamcast, you can apply a CRT filter which adds scanlines and makes everything appear a little fuzzy.

Zero Gunner 2's biggest weakness is its brevity; like so many games of this type, it doesn't take long to see all it has to offer once you become adept enough; if you get a clean run then you can finish all seven levels in well under 30 minutes. The three helicopter types offer some replay value – so does the excellent local two-player mode – and the local high score table gives you the opportunity to better your personal best, but the lack of an online leaderboard does diminish the game's long-term appeal somewhat.

Conclusion

When you consider how much the Dreamcast version of Zero Gunner 2 changes hands for on the secondary market these days, the fact that you can download a superior version on your Switch for a tiny fraction of that cost is worth celebrating; in that regard, you might want to purchase the game purely to feel smug about the amount of (hypothetical) cash you're saving. Perceived value aside, this is a refreshingly unique take on the shmup genre which has some neat ideas but also builds on Psikyo's other good work – the amazing transforming bosses the company is famous for reach their pinnacle here. The biggest problem is that Zero Gunner 2 lacks longevity, even when you take the two-player mode, multiple difficulty levels and (offline) high score table into account. With that said, it's still an essential download for shooter fans and is creative enough to be recommended to those who have a passing interest in the genre but want something a little different.