Geometry Wars: Touch almost has the right angle. Bringing the beloved twin-stick shooter to iPad is one of the best ideas publisher Activision has had in some time - it's fast, fun, and a dazzling display for your eyes.

It deserves to draw some fire, though, for an execution that doesn't fully account for the ergonomics of the device. Awkward controls and a quirky set of features make this adaptation of the Xbox Live Arcade original more of a trapezoid than parallelogram.

Obtuse angle

The issue with the controls surprisingly has nothing to do with moving and shooting. Geometry Wars: Touch splits the screen in half so that sliding your left thumb on the left-side moves your shapely ship, whereas sliding your right thumb anywhere on that side of the screen fires.

This system is completely contextual, so if you move your thumbs across the screen the virtual analogue sticks appear underneath. It's been used before in other twin-stick shooters on iPhone and iPod touch, yet it works particularly well here due to the larger iPad screen.

Only when you reach toward the centre of the screen to detonate a bomb do your realise how poorly positioned its icon is. With your hands at the edges of your iPad holding up the device and twirling your thumbs in the corners, stretching a hand to tap the bomb icon disrupts the action. Setting off a bomb becomes a risk; so much, in fact, that I found myself not using them at all.

War planes

Of course, honing your shooting skills to the point that you don't have to rely on bombs is a tall order given how crazed the action can get. Geometry Wars: Touch brings over six of the original's modes - Deadline, King, Evolved, Wave, Pacifism, and Sequence - plus a new one, Titan. Some are more frantic than others.

Evolved, Deadline, and Wave are your go-to modes when you want to jump in for quick action. In both Evolved and Wave, you're given a number of lives for using on the road to a high score. Deadline provides an unlimited number of lives, though the game only lasts three short minutes within which you're asked to get as many points as possible. It's my personal favourite.

The other modes are objective-based. Pacifism has you aiming for a high score by triangulating a path through destructive gates. Your ship can't fire, so defeating enemies means scurrying through these gates. King mode also limits when your ship can fire. Special circles on the screen denote firing zones, which dissipate after a few moments of use. Sequence is perhaps the dullest of the bunch; it's just a set of continuous levels.

Clash of the Titan

Titan mode - the only addition in Geometry Wars: Touch - nicely rounds out the slate. In it you face giant enemies that break apart and riddle the play field with baby geometric foes. Admittedly it starts slow, but builds up to a frenetic race to obliterate the baby shapes.

High scores are kept via mode-specific online leaderboards. Public leaderboards are labelled as "Friends" scores, but it's just a rundown of the top performers. An option to track user scores via a friends list would be excellent; in fact, integration with a social gaming network would allow that and give weight to the game's dozen or so achievements.

Without these features Geometry Wars: Touch is obviously still playable, though it highlights the game's basic structure. Introducing customisable controls would eliminate the trouble created by the poorly placed bomb button, while expanded online features would give it a sharper edge.