When it comes to twin-stick shooters, the Xbox One now has a fair few titles from which to choose. The excellent Geometry Wars 3: Dimensions is at the top of the pile, whilst less high-profile releases such as We Are Doomed and Sixty Second Shooter Prime bring up the rear.

Puppy Games' Ultratron – the follow up to a $1 Xbox 360 indie title with an identical name - is another such twin-sticker that can be added to the list. A strange combination of Robotron 2084, Defender, and Smash TV, the game tasks you with doing all the usual things you'd expect from such a shooter. You clear screens full of enemies, dodge bullets, occasionally detonate a smart bomb when things become too much, and you collect pickups as and when they're available.

What Ultratron introduces that sets it apart from the rest though, is resource management. The pickups you collect in-game (aside from temporary weapon upgrades) are actually currency which can be used to modify your abilities at the end of each level. So if you pick up $3,000, you might want to spend that on an extra smart bomb or two, or purchase the ability to fire grenades. You may even buy or upgrade a drone pet, which will follow you around and try to help to defend you from the evil robot army. You can purchase up to three of these pets – a "Shooty Pet", a "Rocket Pet", and a "Laser Pet" - and have them all trailing along behind you, taking potshots at the enemy. If they're hit by a bullet, they drop away from your chain and can no longer fire until you've run back to pick them up.

But the most intriguing thing about this little shop of firepower, is that this is where you purchase your lives. Every time you're hit in Ultratron, you not only lose your score multiplier, but also a chunk of your shield. If your shield expires entirely and you're hit again, it's game over. Shields can be replenished in the between-level store, meaning that your success or failure in one level can directly determine how you'll do in the next. What it also means is that there's a cunning game of risk and reward to be had, with decisions to be made. Will you spend your last $2,000 on another shield piece for the upcoming level, or will you take the risk and power up your plasma grenades?

This also makes for an interesting meta-game in terms of the route that you'll take through Ultratron as a whole. The game is never overly-generous with payouts, so the chances of keeping your character alive whilst also levelling up every single piece of equipment on offer will never be within the realms of realistic possibility for most players. With each upgrade costing more and more money, if you ever want to get to the point that you have the most powerful pets or a gun that will destroy anything in its path, you'll need to pick that route and stick to it for the entirety of your run.

Back in the arena, Ultratron is a more than capable shooter. With distinctly retro-styled looks and graphic effects designed to replicate the feel of playing on a CRT screen, everything looks the part. It isn't something that will absolutely wow the crowds but everything plays beautifully smoothly and the action never skips a beat. Relatively short levels mean that you never really notice the amount of time that's passing while you play and when combined with a less-than-punishing difficulty level, this means that one quick go can soon turn into an hour or two of play.

Up until level forty, every tenth level presents you with a boss character to take on. The bosses are simplicity itself to beat on their own, to the point that they may as well not even be there. After the fourth boss, the game turns into a challenge to see how many levels you can survive for before succumbing to higher enemy counts and their ever-increasing speed and firepower. Not only that, but every boss level that occurs from this point onwards will see you facing off against two or more of the individual boss characters. These more advanced boss levels are where you'll most likely see your run end, more often than not.

A generous checkpoint system that saves your progress every ten levels and which allows you to dive back in complete with the money and weapons that you had on your best run through means that the challenge to beat the individual bosses isn't all that steep. The continuing game that occurs after that is what is most likely to keep you playing. The challenge to push yourself further and further through is going to depend on how desperate you are to pick up all the achievements – which will take a few hours of play to collect – and how important the game's leaderboards are to you. Local co-op is on offer for two, so there's some extra playing time to be found there, it must be said. If neither scores nor achievements are your bag, then Ultratron is a short but fun experience for which the $10 asking price may be a tad high. If they are though, you'll likely come back to it again and again, meaning that there's value for money to be had. The gameplay is so perfectly pitched that it's more likely that you'll find yourself picking it up for another hour-long attempt to beat your best score, starting all the way back at the first level. Only this time, you'll take a more defensive route, or you'll try to get all the pets levelled up as quickly as possible, or you'll max out those plasma grenades…

Conclusion

Ultratron is a slick twin-stick shooter with some great and novel ideas at its core. The initially laid out challenge is a pretty simple one, meaning that some players will ultimately be left wanting. Achievement hunters and score hunters will absolutely relish what's in front of them, however.