Tower defence games are getting increasingly popular with developers. It took WiiWare quite a while to get any, but DSiWare's already had three of them (although one is so far exclusive to North America). This latest addition to the sub-genre only really brings one new thing to the table: instead of exclusively defending, you get to be on the attacking side as well.
You play as a new commander on the titular "Libera Wing," an organisation that tries to keep peace across the galaxy. To aid in this, they've installed a number of automated defence towers, but unfortunately some smart new enemies have arrived and they've figured out how to take control of the towers, turning them against the Libera Wing and the people they're trying to protect. Naturally, you must attempt to take these towers back, after which you use them to repel the enemies.
This means that every level is divided into two parts. First, you must safely allow a number of ships to pass by the towers, by moving around your main craft and using it to absorb fire to protect the smaller ships. You can also use a number of items, such as a virus that permanently disables a tower, or a shield that temporarily makes one of your ships invulnerable. The remaining health for all of your ships carries over between missions, so don't get sloppy! During these "primary phases" you'll also get the opportunity to pick up additional items scattered around the field. You can also buy them between levels, but why bother when you can just get enough to clear every stage for free?
Once you've successfully guided your ships to the end, the second part of the level starts. Now back under your control, the towers will be a prime target for enemy takeover once more, which means you can expect a wave of enemies trying to reach the end of the path, just like you did. Each of your towers situated along the main path will automatically fire at enemies, but you can give a number of them some special treatment – your ships can be "attached" to towers, upgrading all of their abilities and allowing them to take enemies down faster. There's also appropriately different items available in this phase, such as a meteor shower, which deals massive damage to enemies in a certain area.
Blowing apart enemies will earn you money, but most importantly, sometimes they'll drop green shards. If you collect enough of these, you'll get an extra small ship to use! They disappear after a few seconds, though, so you should always tap them as soon as you see them. If any enemies manage to make it to your base, you'll also lose money, so try your best to prevent that from happening.
The game doesn't really get that hard until much later. You've got an abundance of useful items which don't carry any penalties, allowing you to clear almost every stage with ease. You'll lose all of your items after each chapter, but you'll get plenty of new ones back so fast that it hardly matters.
Between every level, you'll get a whole bunch of dialogue explaining what's happening, and giving you information on new items and enemies, but for the most part it's all pretty boring. The fact that there's a multitude of spelling and punctation errors and all characters look fairly amateurishly drawn doesn't help things much! Luckily, you can skip every single one of these conversations, if you'd just prefer to get down to the action.
The graphics and music are quite uninteresting, too. As already mentioned, the character portraits look quite bad, and the graphics during actual gameplay are bland and not likely to impress much. As is usual with these kinds of games, there's not much music to speak of, but what's there is totally forgettable.
With 36 main campaign levels and 24 additional "quickplay" levels, each of which consists of an "action" and "defense" part, you'll be content for a decent while if you're just looking for more tower defense action and have already exhausted DSiWare's other options. If you're just looking for the best game, though, then it's best to stick with Starship Patrol/Defense.