The demo offered a tutorial stage that introduced the basic controls and the Celestial Brush. The brush is brought up with L or R -- either tap to toggle or hold down. This puts the brush interface on the bottom screen, where the player can then draw on the screen directly. The top screen displays an inkwell indicating the amount of ink left. The first task with the brush is to restore a destroyed bridge, accomplished by drawing a rectangle over the broken area. Some areas were clearly crumbling, requiring Chibiterasu and Kuninushi to walk one at a time for weight reasons. In the beginning of the game, you must separate the two with X and then walk Chibiterasu across the passage, usually to a switch that creates a sturdy bridge.
Chibiterasu and Kuninushi then moved on through a gate into a path of stars, where they met some new Brush Gods -- an adult penguin god and three baby penguin gods, who gave me the Brush power to draw a path for my partner to follow. This immediately came into use in a more complicated switch puzzle, in which I first had to move Kuninushi across a fragile area of land to push a switch, then go over the resulting bridge and press another switch to open up another path. After this, I was drawn into a random encounter with some dancing enemies. The controls here are pretty simple: X to dodge, Y to attack, hold Y for combos. Following this brief fight, I was then given the Power Slash ability by the returning Rat, though I was rushed out of the demo area before I could mess with it.
Overall, Okamiden feels a lot like Okami, but a lot faster-paced and with new puzzle elements. Or, to put it in terms of knee-jerk internet reactions, no, Capcom didn't ruin Okami by putting it on the DS. At least not from the outset -- since I only played a bit, there's plenty more game that might be ruined.