In Defence Wars you got a bunch of turrets, cannons and tanks to defend you against oncoming armies, but D-Tank takes its name quite seriously and only has one of those, the tanks. You control one single tank at a time as you roll around arenas of varying size, either defending your base from the enemy forces or attempting to take out the enemy fortifications instead.
The game is divided into three difficulty levels, but this doesn't just make you weaker or anything; each actually has eight different stages to play. In each set of levels, number four and eight are attack missions, while the other six are defence ones. The basic gameplay doesn't differ much between the two, you just move around as a little tank, taking out other tanks, bigger tanks, drilling machines and whatever else attempts to destroy your HQ. Some enemies will go straight for the HQ, totally ignoring you, while others will actively attack you first, so you'll have to do strategising on the fly to decide what you should destroy first.
Thankfully, getting hit by something isn't necessarily fatal. Your tank will be blown up, but you've got an infinite supply, so you'll simply spawn in with a new one. Repeatedly dying will however lower your score at the end of the level, so if you're a highscore maniac you'll want to avoid doing so as much as possible.
Initially, it might seem strange that D-Tank is played with the DSi's buttons rather than the touch screen, but the moment you start it will quickly become evident why: it simply has too many actions to work well in conjunction with the stylus. The shoulder buttons turn your tank in fixed increments, while A fires your primary weapon. B drops mines, which will explode the moment an enemy touches them, but you can also hit them with your primary weapon to detonate them prematurely. Mines regenerate the moment they explode, so you can practically use them endlessly, you just can't drop a ton at a time.
Your standard primary fire is pretty weak against anything but regular tanks (although destroying one does cause an explosion that can damage or destroy other enemies), but luckily there are plenty of powerups scattered around each level when they begin. They stay around indefinitely, so you can just leave them on the floor until the best moment. They include a blast cannon, pulse cannon, machine gun and shotgun, so pick wisely, as some are better in certain situations than others.
In the attack levels, your objective is simply to destroy an enemy base. The only enemies in these levels are a bunch of stationary turrets, all of which can be blown up in one hit with mines, so they're generally a breather after the more action-packed defence levels.
The game only has 24 levels, but they can take quite a while to finish, with over 200 enemies appearing in each of the levels in the last set of 8. Nothing is unlocked for clearing all 24, but of course you can attempt to improve your highscores on each set if you wish.
Like most of the GO Series titles, the game is pretty simple graphics-wise, but the graphics fit the gameplay nicely. Every group of four levels from all three level sets has different music, so there's some nice variety in the audio department, and it helps that all the tracks are moderately catchy as well.
All in all, D-Tank is another worthwhile entry in the GO Series, costing only 200 Points yet providing a good hour or two of fun, with potentially even more if you're going to be increasing your high scores afterwards.