The advent of high definition entertainment has been great for some things - like nature documentaries and sci-fi movies, where colour and detail pop on the screen - but alarmingly revealing for others.

Grizzled actors and make-up-caked actresses don't fare so well in the high-resolution lens. Pamela Anderson looks pretty good in standard resolution, but the years show right through the make-up when seen in HD. Edward James Olmos may have a special spot in any sci-fi fan's heart for his roles in Blade Runner and Battlestar Galactica, but I can do without a high-definition close-up.

Even though TowerMadness HD seems a natural fit for iPad with its sci-fi tower defence gameplay, this is an experience that likewise doesn't fare so well in HD.

Sheep's ready for her close up

It takes only a moment to understand why TowerMadness HD has difficulty making the transition from iPhone to iPad. The graphics - impressive on iPhone in all their 3D glory - evoke no sense of wonder on iPad, with flat textures and crude polygonal objects. The up-scaling process has not been kind.

Putting the sub-standard presentation aside is tough, although the solid tactical gameplay works overtime to capture your attention.

Charged with protecting a flock of sheep, you're pressed into plunking down various turrets to deal with alien invaders hoping to snatch away your herd.

Laser cannon, rail gun, guided missiles, and a handful of other turrets can be deployed to deal with different extraterrestrials. Flying Aliens succumb to anti-air turrets, whereas basic Grey Aliens are best eliminated with shots squeezed out of a rail gun.

Affirmative action

Variety is chief among the game's strengths, and with 28 well-designed maps within which to try out different tactics, you're sure to stay busy. Frequent boss battles test your skills in planning and patience. Learning how to survey open-ended levels and make the most of fixed path stages gives TowerMadness HD a diversity that few in the genre have.

Much effort has gone into making TowerMadness HD a compelling proposition on iPad with the introduction of new maps and split-screen multiplayer. The multiplayer is intriguing, though not particularly successful.

With the screen divided in half, you and a friend compete for the highest score on any of the maps unlocked from the single player campaign. You're given the options of sending waves early, speeding up your competitor's aliens, or even stealing their sheep by spending money.

You're usually so busy holding your ground against the aliens that these extras are a secondary concern.

A matter of priorities

Instead of split-screen multiplayer, investing development time into improving the graphics and integrating with an existing social gaming network such as OpenFeint or Scoreloop would have been preferable.

TowerMadness HD offers some of the features that come with these networks, but the leaderboards are clumsy and replay videos are practically hidden because they're buried so deep within the system.

When it comes to gameplay, though, TowerMadness HD does deliver good tactical action. Despite the much-appreciated effort to tailor the game to iPad with new content and up-scaled graphics, there's a distinct sense that it felt more at home on iPhone and iPod touch.

It's worth remembering that just because you can go HD, doesn't mean you should.