It was only a matter of time before the humble crab made his debut in an app game. Avatars in portable games are often in a state of perpetual motion, and usually moving from one side of the screen to the other, so a creature known for his sideways toddle is a perfect fit. We join the eponymous shellfish as he rescues younger crabs in increasingly elaborate environments. Whether you’re ascending trees, sandcastles, pebble structures or twig buildings, the object is always the same: run from left to right (or right to left), collect friends and avoid foes. The only control is to tap the screen to jump, so it’s all about timing. Ascent is always in an upwards spiral, which can get dizzying (and I was playing it at a desk, not bobbing along on public transport), but the charming graphics help somewhat. Mr Crab himself is endearing with his buck teeth, big eyes and variety of hats (from bowler to party). And he never shirks from his crab-rescuing responsibilities. That would be a little shellfish!