Classroom experiments as a teaching tool increase understanding and especially motivation.Traditionally, experiments have been run using pen-and-paper or in a computer lab. Pen-and-paper is time and resource consuming. Experiments in the lab require appropriate installations and impede the direct interaction among students. During the last two years, we have created fully elaborated packages to run a complete course in microeconomics principles using face-to-face experiments with mobile devices. The experiments are based on Bergstrom-Miller (2000), and we used classEx, a free online tool, to run them in the classroom.The packages were used at Universitat Pompeu Fabra with over 500 undergraduate students inthe fall 2016. This paper presents our experience on classEx and the Bergstrom-Miller approachworking in combination, and the lessons learned.