We were first introduced to Desktop Tower Defense (DTD) years ago from a twit.tv network pick if the week link here. DTD is a strategy game where you have to protect your desktop from invaders, better known nowadays as "creeps." There are different types of towers with which to defend yourself: Pellet, squirt, dart, swarm, frost, bash, ink, snap and boost towers. Pellet towers are the cheapest but they also do not offer much defense. Squirt and dart towers do more damage but are also more expensive. Frost towers slow down the creeps in order to provide more "fire time" for the towers. Ink towers throw down a big blob of goo that damages creeps. The pellet, squirt and frost towers are my wife's favorite defenses. For each level of defense, there is an equal level of creep. Normal (the easiest to destroy), Immune, Group (wife thinks these are a pain in the patoot), Fast, Spawn, Flying, Morph, and Dark. DTD allows you to customize towers and creeps to your liking via the DS touch screen.
There are three difficulty levels in the handheld game - Easy, medium and hard. Easy is 30 rounds of creeps with one entrance and one exit. Medium is 50 rounds of creeps with two entrances and two exits. Hard is 60 rounds of creeps that are 50% more difficult to destroy than in the easy and medium modes. This level also features two entrances and two exits (and my wife has been able to defeat this level after many hours. I'm still try defeat medium).
All in all, this is a decent alternative to the web game. The towers are a little slower to upgrade in the DS version compared to the web version but this is easily handled by upgrading after the creeps have either been defeated or have escaped. This would be a great game to take with you on a driving or plane trip. It keeps the passengers (ages 7 and over) hooked from the get go. My wife is 40 and she can't put it down. Might have to get her a DS all her own just so she can play it. NAHH!!!
