GearSketch is a learning environment for the gears domain, aimed at students in the final years of primary school. It is designed for use with a touchscreen device and is based on ideas from drawing-based learning and research on cognitive tutors. At the heart of GearSketch is a domain model that is used to transform learners' strokes into gears and chains, animate the turning of the gears and check whether learners' solutions to practice problems satisfy the given constraints. Additionally, this domain model is the basis for GearSketch's learner model and item generation an selection mechanisms. The learner model is used to track learners' knowledge and adaptively select items as they progress through the practice problems. Two experimental evaluation studies show that GearSketch's interface and animations lead to improved learning outcomes, but that its adaptive features do not significantly affect posttest results.