Ok, so yeah a review of a demo is kinda lame, but I played it for a while yesterday, and I figured I'd say what I thought.
Premise: Magnetica is a puzzle game... a random assortment of marbles are sliding down a track, and somewhere within that path (always near the end point) you have a little launcher-thingy, from which you can fire off new marbles. Using the stylus, you flick the marbles where you want them to go, and off they fly! Get three marbles of the same color together, and they vanish. If the lead marble on the track reaches the end-point, it's GAME OVER!
Gameplay: As puzzle games go, this one isn't too bad... if you have groups of like-colored marbles, seperated by others, you can remove the ones in between, and the "magnetic attraction" will pull the similar ones together, creating chain-reactions ("chains"). However, that's about the only "extra" move you can do... you're just flicking marbles at other marbles, until you get rid of them all, or they reach the end-point. Within the demo, there were 2 different boards (1 for the regular challenge mode, the other for the "quest" mode)... which did add some variety, but not as much as i would have liked to have seen. Quest mode also featured a few items (beyond the very few within challenge mode), but none of these served to keep the game interesting for long.
Overall: Graphics were pleasant, but not in the way of playing the game. Sounds were not impressive, but not annoying either. Gameplay was never very exciting, sadly. All in all, you'd be better served with Meteos.