Vector TD (iPhone)

The concept behind vector graphics enables scaling of any magnitude. No matter how close you zoom in, whatever you're looking at is guaranteed to be sharp.

In the case of Vector TD, however, there's a glitch in the scaling down of this accomplished tower defence game. While it retains the same thoughtful tactical gameplay that makes the PSP minis version a blast, the smaller, crowded interface on iPhone and iPod touch makes it an inferior version.

Holding the Vectoid invasion at bay is harder here on the smaller touchscreen, even though the fundamental gameplay remains untouched. Vector TD struggles to display all the necessary menus and panes of data while preserving space for the action.

Windows can be collapsed, but the need to constantly access build menus, for instance, forces you to leave them open more often than not.

Additionally, the scaled down buttons make interacting with menus a tricky affair. You have to be deliberate in building towers because it's easy to accidentally select the wrong one or construct it in the incorrect spot.

Ironically, it's exacerbated by the variety of towers available for construction. Blueprints for 11 different towers enable you to devise pointed strategies for defeating a host of geometric enemies.

Plopping down a red refractor easily whittles away red foes, while green lasers are cheaper and more effective against like-coloured enemies.

Saving up for an expensive purple power beam means having a strong defence against all kinds of enemies, but you have to account for a slower rate of fire. Each tower can be upgraded through ten levels.

You're free to plot the placement of towers in each of the game's eight levels, which are split among Beginner, Normal and Extreme difficulty modes. The layouts vary from winding mazes to stages with two entrances through which Vectroid forces can stream in.

The length of every level is standardised at 50 waves, which guarantees consistency even though it's longer than I'd prefer. Shorter 30 or 40 waves stages would eliminate the feeling that levels are drawn out for the sake of extending game time. Similarly, it would allow the action to ramp up earlier and improve portability.

Such considerations prevent Vector TD from being an ideal iPhone and iPod touch adaptation, though it's still a worthwhile play.