Clear Structure: systematic, integrative, and differentiated acquisition of basic knowledge in the main learning area with "Test yourself!" pages. Connection with the second learning area and parallel differentiation on the support and promotion pages. Training for class tests or project proposals on Fit in. Core principles: diagnosing, differentiating, teaching skills. Free online diagnosis. Consistent differentiation at various levels. Transparency of learning: advance organizer, self-diagnosis. Process-oriented preparation for class tests. Independent and cooperative learning. Information on the series edition: clear structure, systematic, integrative, and differentiated acquisition of basic knowledge in the main learning area with "Test yourself!" pages. Connection with the second learning area and parallel differentiation in the support and promotion pages. Class tests.