Book excerpt: Motivate your students to break out of their "fog" and focus on problem solving and learning with these 30 easy-level brainteasers. They include a variety of topics from riddles to math problems and are great tools for building critical-thinking skills. Each BrainStarter requires very little time and no setup, making them easy to incorporate into your daily plans. You can also try them with the entire class or as quick team-building exercises.