Not so long ago, the App Store was overrun with tower defence games.

It's not surprising really. The genre's discrete levels were perfect for bite-sized mobile sessions, and the overhead viewpoint provided a tactical vantage point without placing undue stress on an iPhone 3GS's silicon.

But the emergence of a handful of supremely accomplished tower defence franchises soon stemmed the tide of tower defence wannabes.

Once iOS gamers got their teeth stuck into the likes of Anomaly Warzone Earth and Plants vs Zombies, it was hard to go back to the also-rans.

A challenger appears

Aspects TD is the latest challenger to these incumbent kings of tower defence, offering familiar gameplay with a multiplayer twist.

A po-faced campaign serves as an introduction to these two-player face-offs, which see you dispatching offensive troops as well as peppering the path to your own base with defensive turrets.

But for some reason, Aspects TD doesn't allow you to upgrade your defensive structures, and by eschewing this staple of the genre, the game suffers. Since you can't beef up your defences at tactical chokepoints, the most obvious strategic recourse is to simply fill the screen with missile launchers, gun turrets, and lasers.

Attacking is a similarly simplistic and gung-ho affair. Sending troops to besiege your opponent is a matter of dragging the relevant icon from your toolbar, and once you've dispatched an armoured grunt or a flying gargoyle, your forces automatically march towards your adversary's fortifications.

Looking elsewhere

As such, the tactical core of Aspects TD isn't to be found in the act of either attack or defence - it's in the tension between spending your resources on offensive troops or defensive emplacements.

Tower-placement undoubtedly plays its part too, but with a limited selection of turrets on offer and no upgrades to pursue, matches are hardly strategic chin-strokers. It's disappointingly basic, and battles soon start to feel like wars of attrition fought on bland, featureless grids.

Aspects TD may offer creative character designs and technical competence, but that's no longer enough for veterans of the mobile tower defence wars.