In Drawing with Stars I did not want a toolbox but a more direct experience where you can do everything directly with your fingers without the need of selecting a tool. I also wanted that one can use the full screen without having a toolbox that displays or pop up somewhere. This may have some drawback but my primary goal is to offer a simple toy where nothing interrupt the drawing.
So I simplified everything, the first user task is to draw stars so as soon as you put your finger (when no stars exists) you draw stars until you put it off. Second task is to remove some stars, so if you start your finger movement on a star it will remove the stars under your finger (you are in "remove mode" until you remove your finger). And if you want to start over and remove all the stars, you just have to shake the device.
But sometimes you want to add stars where some stars are already displayed. Several solutions were available to force the addition of stars : use two fingers (but since I wanted to handle drawing with several fingers it was not possible), double tap (was not straightforward and the first tap on the screen was difficult to evaluate). Eventually, I choose another solution : if you keep your finger stationary for 1 second, the stars that you have removed fly back -which offers a nice animation- , a star is added (and you hear the sound of the new star ), and you are in "add star" mode until you put your finger off the screen.
Users testing was interesting because people are used to have tools and lost of them don't understand at first shot how it works. But once they understand, they love that they don't need to switch tool to do what they want. For the children, it was not a problem because they play directly with the tools (see some stars animations seems to be their main goal eventually!)
UPDATE: finally I needed some tools ;-) For example people wanted to do a snapshot or adding a background image. So I've added a "moon" sprite, and when you click on it, a menu appears...But since I've got a menu, I've added some options such like changing the stars size or colors and now it is not very convenient to access these options... Anyway, I still want the toy to stay full screen without tools....
If you have some suggestions/ideas to enhance the experience, you are more than welcome!