Just when you thought developers had grown weary of churning out cute, Cut the Rope-style physics-puzzlers, along comes another one to steal our spare time.

Rescue Roby HD breaks little ground in a genre so saturated that it should come with its own flood warning system, but the undeniable charm of its robot cast and mostly gentle puzzling means it should be a hit with the casual crowd - well, for the hour or so it lasts anyway.

Bot or not?

Although other characters get introduced over the four stages, the story tugs most insistently on your heart strings with its tale of Roby, the defective robot, who needs your help to avoid being scrapped.

Each short, but generally sweet, stage involves you strategically removing clutter like crates, planks, and the odd box of explosives to ensure that Roby tumbles safely into a delivery box.

There's a lot of trial-and-error involved, but the best stages are undoubtedly those where you can meticulously plan out a solution to ensure Roby will pick up all three stars by setting in motion a complex chain of tumbles and rolls.

Removing obstacles involves simple taps, and while failure is common the brevity of the puzzles means you're unlikely to give up.

And once Roby starts having to work in tandem with another character - such as his equally defective girlfriend Miss Understood - to ensure that both make it out of the factory, the game becomes just head-scratching enough to stay challenging.

Back in the box

Although the looping music can grate on your eardrums, the presentation of Rescue Roby HD is both simplistic and rather warm and welcoming. This is mainly down to the characters, whose plight and expressive goggle eyes are hard to resist.

Only the last levels and their magnetic robot fall flat, mainly because cuddly Roby takes a back seat to a more futuristic machine.

It's all over way too soon, too - especially if you're an old hand at physics-puzzlers. Still, the developer has promised a generous 100 more levels with Miss Understood for Valentines Day, so Roby shouldn't be consigned to the gaming scrapheap just yet.