Star Wars: The Battle for Hoth is a tower defense-style game originally released for the iPhone and ported to the Windows Phone 7 platform. It's a fun game in concept, but technical issues and an inconsistent difficulty curve make it more frustrating than fun in practice.
The game is based on the battle that starts the second Star Wars movie (not the fifth, the second), and is fairly standard for a tower defense game. You place your rebel forces around a mostly-open level to destroy Imperial units as they attempt to make their way off the right side of the screen to attack the unseen rebel base. Enemies range from Imperial probe droids to the mighty AT-AT. By digging trenches and strategically placing units, you channel the Imperials around the level to expose them to as much rebel fire as possible. However, the Imperial units have their own arms, and they will take shots at your units to weaken and destroy your defenses.
My personal bane of tower defense games are the units that are both fast and heavily armored. The units that fulfill this role in SW: Hoth are the armored AT-STs. Many a level went by perfectly up until a final wave of a mere pair of AT-STs walk past a screen full of units and reach the end intact. It's more than a little disheartening to see your best defense come to naught. These units are introduced after only a couple levels, meaning you have to plan for them on nearly every level. And planning for them can be difficult when you have to spend a good percentage of your "command points" re-building units that are destroyed by attacking Imperials.
The game has serious control issues. It seems to be unable to tell the difference between a tap and a swipe — or, at least, it takes everything as a swipe. It's as if, unless you manage to tap a single pixel, the game assumes the multiple points you touch are actually part of a movement, not a tap. Nowhere was this more apparent than on the level select screen, where only the lightest pinpoint touch would select a level instead of scrolling the level list by a pixel or two. (A title update eventually fixed the level select screen, but gameplay controls weren't improved.)
On the flip side, when you do perform a swipe, the game sometimes registers a tap. This happens frequently when panning the board or pinching to zoom out — at the end of the swipe or pinch, if one of your fingers happens to rest over one of your units, you will likely find that unit selected, centered, and zoomed in upon. Imagine the frustration when, every time you pinch to zoom out, the game immediately zooms back in on a unit you didn't want to select.
Generally, it has all the fun (and sometime-frustration) of a standard tower defense game. The sounds and cutscenes directly from the movie add to the flavor. The difficulty of some of the enemy units (and their ability to destroy your units, sometimes in a single shot) give it a harsh challenge. But having to fight the controls makes it a very difficult game to deal with.