The day when all ideas are finally wrung out of iOS physics games will be a harrowing one, but for now we're safe in the arms of Cart Cow - the physics-based cow game that combines cattle, UFOs and clover collecting as part of a rag-tag premise likely based on nouns pulled out of a hat.

Your role is to build platforms across the screen by drawing lines, then guide a cow sat in a shopping trolley to the exit while collecting clovers positioned in key areas around the level. It's a marriage of momentum and gravity that often results in a cow being hurled out of its ride. Falling out of your cart might not be a game-ender, but bonus points are given based on whether or not you stayed in for the full level. While the controls aren't particularly difficult to handle, the primary challenge lies in speed and planning.

Line placement in particular can be tricky. Later levels require slightly more lateral thinking when objects like UFOs and rockets start to be added, both of which affect how quickly and where exactly your trolley will go. UFOs can beam your cow to different platforms, granting the game a very faint but impressive Portal-lite quality as the cart trundles through the green beam of one flying saucer, and then out of the pink beam of another ship perched over a higher platform.

But even earlier levels are challenging enough to demand a few repeat playthroughs. Cacti and trees have been strategically planted around the screen and can block your cow's path if you've been careless with your line drawing, but the game has a user-friendliness often missing from basic physics titles, and misdrawn lines can be instantly reset with an Undo button. Even the pacing of the game is toyed with via the introduction of mules, who speed up your cart by kicking it as you roll past.

Unfortunately, the game stumbles on technical issues just as quickly. Reloading has a tendency to be slow on the slow side, and in situations where you're only looking to restart a level and grab that last clover the seconds feel like they tick on into minutes. Still, it's testament to the quality of the game that you'll likely overlook the occasional tedious issue to replay old sections in a compulsive bid to collect points.

Despite being yet another physics iGame, Cart Cow shouldn't be lost in the fog of similar titles. While it lives in danger of being filed away in that section of your brain that stores vague memories of forgotten train timetables, it's a surprisingly clever game that deserves to be played.