I am of the opinion of all the comments. Clear and beautiful models explanations. We are tempted to skip steps to realize immediately the models that we like the most. But as a beginner, stages, ordered by difficulty, must be strictly kept otherwise it quickly becomes disillusioned. Finally, we must be patient, follow the steps even if it weighs us (as for reading). A perfect activity to learn to focus and relieve stress of the day. This activity is also great for children (from 9 years) who get caught in the game of intertwining cords and learn to focus their energy (girl or boy). Ideal for the toughest spot.