There are few better things in video games than a satisfying upgrade loop. A new axe that chops trees twice as fast as your old axe — or a jetpack that makes you realise you've only experienced a fraction of the game world despite hours of exploration — can be incredibly rewarding, and it's this sensation that SteamWorld Dig 2 does better than most. 

In a beautifully detailed steampunk-cowboy world, players take the role of a robot named Dorothy, whose quest to find her lost pal leads her deep below the surface to glittering mines, glowing fungal forests, toxic human settlements and fiery lava-filled ruins.

At first you only have a pickaxe to make tunnels and the ability to climb nimbly up vertical walls. Just the act of digging alone is surprisingly fun, as the size and shape of the tunnels you dig is entirely up to you, and everyone will chart their own unique course down through the dirt.

Sooner or later though your lamp will run out, leaving you all but blind. Thankfully many dirt tiles yield gems and precious metals when dug, and returning them to the robot town on the surface will net you cash to buy upgrades, like a better lamp.

This loop of digging, returning, selling, upgrading and repeating is extremely gratifying — as each new lamp, pickaxe or other equipment will get you a bit further, to places with more valuable loot, before you have to return — but Dig 2 has a lot more going for it, with handfuls of platforming, roleplaying and puzzle elements thrown in to the mix.

Upgrades found underground impart entirely new ways to traverse, explore and dig. Early on Dorothy gets access to a grappling hook, which not only gives access to previously inaccessible areas but changes the way you approach your digs, and this is true of later more unexpected upgrades too.

Hidden caves contain puzzle rooms to overcome that make an excellent diversion from the main game. Each themed challenge must be understood and overcome — not unlike the shrines from Zelda: Breath of the Wild — before you can claim its treasure, but many also have secret objectives you can only complete if you come back later with better gear.

Most of the time, the reward for completing these caves are cogs, which empower you to tweak your robot's build to suit your playstyle. What I love about this system is that you can move the cogs around at any time, so unlike a traditional RPG you don't have to commit to upgrades permanently. If a new enhancement becomes available and costs four cogs, you can simply strip them from four one-cog enhancements you can live without. 

Throughout the world, creatures and enemies lurk at every turn threatening to dismantle you, and each kind is a sort of puzzle of its own that you'll learn to defeat (and exploit) as you go. Unlockable vacuum tubes let you zip around between discovered areas easily, but the constant allure of treasure meant I ran through my old tunnels the long way dozens of times.

What makes Dig 2 so very good is how tightly the various upgrade systems are tied together, with every aspect being fun enough to be its own reward but also propelling the player forward. Digging through the main areas will score you the upgrades you need to progress and finish the game, but grabbing materials will get you the cash for better gear to let you dig more efficiently.

Meanwhile defeating creatures increases your overall level, unlocking cog perks that make things easier, more challenging or just more fun (and of course, you need to play those optional caves to get the cogs that power those perks).

I'd go so far as to say Dig 2 hits this mark better than Metroid: Samus Returns, the most recent entry in the series that innovated this kind of game. With a flimsy-but-fun narrative premise and rock solid platforming gameplay backing it up, the rhythm of exploration and upgrading here is about as addictive and satisfying as they come.

Steamworld Dig 2 is out now for Switch (reviewed), PlayStation 4, PlayStation Vita and PC.