Difficulty Level 3 With 24 hidden treat compartments, the Nina Ottosson Challenge Slider dog treat puzzle is one of our most challenging puzzles yet! Nina Ottosson treat puzzle games are a great way to engage your dog's mind with challenging and rewarding activity. The Challenge Slider will keep your dog´s mind busy with 24 treat compartments. In this game dogs must move each slider, one at a time, in different directions, to reveal hidden treats or food. Slide, treat, and repeat