ArtePiazza, developers of classic Dragon Quest games and Opoona, have a DSiWare tower defense game too. Arrow of Laputa sticks to the formula of monsters scurrying down a winding path while sessile soldiers swing swords and shoot at them.
The DSiWare game has your basic five unit types: soldiers, archers, mages, knights, and (the most interesting of the bunch) hammer soldiers with eye patches. Units can be upgraded with extra skills and you can earn more skill points if you stand next to one of those colored heaven stones.
Arrow of Laputa has sixteen stages with slimes, goblins, and bats to battle. The DSiWare game costs 500 DSiWare Points($5) and is on Japan’s shopping channel now.