I found this game very dissapointing.
The basic idea is that you get a picture on the top screen of the DS and an outline of it on the bottom screen. You then have to use the stylus to colour in the picture to make it look like the one on the top screen. There are various tools available including pencil and watercolour. However I personally couldn't see the difference between the two.
The colours that you use on the bottom screen do not seem to match those on the top screen and it seems to take a long time to colour in one section of the drawing. It is also difficult to stay within the lines as the colour doesn't seem to go where you want it to.
Another disappointing feature is that once you actually manage to complete a drawing you are only able to save 5 of them. So after you have completed 5 there seems little point in doing any more.
Basically...get a pencil and some paper, i think it would be more fun and a lot easier.
After fancying something slightly different for my DS, I bought Paint by DS - it was only £8 so I thought even if it was rubbish I wouldn't be wasting any money.
The basic jist of the game is to copy a picture from the top screen using various colouring methods with the stylus - watercolours and pencils etc. It's meant to be good for artists and good for just sitting and relaxing.
I honestly don't know why someone thought of this game, but they needn't have bothered.
It's almost impossible to get the colours the same as the ones you're meant to be copying, and the colour never seems to go where you want it to! Another downside is that, should you actually do enough pictures to save any, you can only save 5. Which for a DS cartridge, seems like very little.
I spent about an hour on one picture, only for it to turn out looking like a 3 year old's picture.
Overall, it's a very disappointing game, although maybe I'm just no good at art!