There’s an alarming trend creeping into iOS gaming - one that hasn’t been seen since the heyday of the arcades.

Instead of carefully balancing the challenge in their shiny new apps, some developers are ramping up the default difficulty and offering to sell you assists and extra lives when you inevitably get stuck.

Ironworm is guilty of this fun-sapping trick. It’s crushingly difficult, and relentless with its in-app purchase badgering, which is a shame because there are some interesting innovations underneath the ugly veneer of a poorly applied freemium model.

You play as the titular Ironworm, a sort of heavy metal pastiche annelid with the face of Tommy Iommi and the bottom of a spiky wrecking ball.

You have to attach yourself to each level’s platforms using your teeth, then swing the spiky end at the floating baddies. If they hit your fleshy white body, you lose a life. Lose three and it’s all over.

Swing Thing

As a premise, it’s great: well-suited to the format, built around a solid idea, and featuring genuinely innovative worm physics (not something I ever thought I’d write).

The problem is, Ironworm is so irritatingly difficult that it's almost impossible to enjoy its finer qualities.

There’s nothing wrong with tricky games, but when you’re facing an onslaught of enemies and projectiles and you have such a cumbersome control method to deal with, the results are always the same – phone-hurling frustration.

For every satisfying swing or defensively stout spike-ball smash, there’s a life lost while you desperately tug at the screen with your finger trying to get the stupid worm to move off his little perch.

It’s doubly annoying because you can clearly see how Ironworm could be fun. Even if every level had just slightly fewer enemies, or you had a couple more lives, you could spend the right amount of time getting the hang of the worm physics (which are oddly meaty and tangible, to the point where they’re almost a bit disgusting) and actually develop some tactics.

But this isn’t a game that wants to encourage you - it wants to punish you and take from you.

Metal Hammer

The whole package pays homage to the same world of metal that Brutal Legend so artfully recreated, with a thrash soundtrack and plenty of references to hell and blood and all that nonsense.

If the game wasn’t so wall-kickingly irritating all this stuff would be quite charming.

In-app purchases are a perfectly valid and necessary way to do business, but when they actually get in the way and end up dictating the very design of a game then they’re just horrible. There’s a good game hidden in Ironworm. You just might not have the cash to find it.