Tecmo have finally dipped their toes in the DSiWare water with a couple of games that have the novel feature of being played holding your DSi upside-down with the touchscreen at the top. This first one is based upon the classic Tekhan vertical shooter Star Force, which was one of the Virtual Console Arcade launch titles on the Wii. In both graphics and sound it's quite similar; the main difference being that players control the waves of "enemy" fighters and boss ships through a series of levels in which they're trying to destroy the "player" ship at the "bottom" of the screen (we really need more inverted commas in this one).
The touchscreen is at the top because the action is controlled with the stylus and presumably the developer wanted to maintain the appearance of the game as if it was being played in an arcade. The computer controls the ship in what is now the lower screen with a three ship reserve, moving back-and-forth and firing up at your armada. Ship waves are initially shown as ghosted images, only coming to life after players tap them and then trace out a brief pattern for them to follow into the lower screen where you hope they'll collide with the AI ship. You'll get to control a wave of stationary ships that fire when tapped and can moved by keeping the stylus on the ship and dragging it around after tapping it. If the AI ship invading your base gets past multiple waves of your defenses you get to control a boss ship: firing one or more guns by tapping them and moving the ship by tapping and holding the stylus as with the smaller ships.
Every time you destroy three ships the level increases and every five levels the stage changes with new backgrounds and ship sprites for you and the AI. If you manage to hit your target consistently you may never use the stationary shooters or boss ship, but that's not to be expected because like any shooter there's power-ups and bombs for your opponent to pick up and use against you. If The AI destroys your boss ship in any of the boss battles it's game over for you and, unlike the computer, you don't get to put in another credit to continue (though your top scores are recorded for posterity).
After level 15 the background becomes a star field and the ships from the previous three stages appear in various combinations. We managed to get to level 20, but were finally destroyed so we don't know if that's the last level or not. It certainly seems likely that there are only three distinct stages all told and then this final amalgamation of the earlier ones; which really isn't bad for a 200 Point release like this. Of course being the baddie is a bit easier than taking on the traditional role of lone ship against the armada, but if you've got a friend around you might have a more challenging time. Gameplay is exactly the same, only players face each other with the D-Pad and buttons being used by the invading player to shoot down waves sent at them by the other player - clearly the larger screens and increased viewing angle of the DSi XL will be advantageous for this mode.
Tecmo have been pretty good about bringing their WiiWare releases to other territories, no matter how Japanese they may seem, so we have every reason to believe that this funky upside-down version of Star Force will show up in other DSi Shops eventually.