RGB Express features cute little trucks tootling about in a cute manner, delivering cute little coloured boxes to cute little buildings. You might have noticed a theme here.

What won't be so obvious from this game's jolly, vibrant façade is the sting in its tail.

Initially, though, everything is extremely straightforward. You're tasked with delivering a red box to a red building, achieved by dragging a line from your truck to the box and then to the building, and then finally pressing 'play' to set your plan in motion. Easy!

Next, multiple blue boxes have to be delivered to multiple blue buildings, along rather more winding roads. Still easy! This, you think, is going to be a breeze.

Box clever

But RGB Express is easing you in gently. As you work through the challenges, the restrictions imposed on you become clearer. Trucks can carry a maximum of three boxes and you cannot use the same piece of roadway twice, unless you're crossing over it.

Your delivery attempts are also instantly terminated if two trucks collide or one has the temerity to show up at a building with the wrong box or no box at all.

With several different coloured trucks in play, you must therefore increasingly make clever use of crossings and corners, turning routes and roadways into a kind of multicoloured geometric spaghetti.

Later, switches enter the mix, raising and lowering drawbridges as a little truck trundles over them; white trucks arrive that are capable of carrying boxes of different colours; and drop-off zones appear, enabling a box to be strategically dumped on the roadside, for later pick-up.

Eventually, you'll find yourself staring at seemingly impossible set-ups of trucks, roads, buildings, and boxes, experimenting with crazy, convoluted routes, in order to get your boxes to their destinations without any disasters.

Trucking good

Everything about RGB Express screams care. The visuals are bold and bright, and the pleasingly tactile interface is intuitive. As you work your way through the game, cut-scenes show your little business growing, and when you’re dragging a route for a truck, others show their positions at that point, aiding planning.

The way levels are unlocked is especially well-considered. Instead of all-too-common brutally linear progress, levels are unlocked as cities which contain batches of ten puzzles.

These can be played in any order, and completing one awards you coins, which are then used to unlock new cities. You can jump ahead to any of the game's six chapters if you've the funds and fancy a sterner challenge.

In many ways, RGB Express feels like a modern incarnation of iOS classic Trainyard. And while even the toughest levels here aren’t quite as merciless as Trainyard's, you'll still find yourself scratching your head for a good long while after blazing through the initial cities, thinking it was all going to be so very easy.