The demand for computer programming professionals in STEAMrelated areas has rocketed in the last decade. Initiatives such as the Hour of Code or CodeWeek take advantage of online platforms like Code.org to reach millions of students through a one-hour introduction to computer science and computer programming. Despite the excellent curricular design of Code.org courses, we believe that learners could benefit from a platform where they can create their own programming challenges that can be shared, assessed and remixed by the rest of the users. We named this platform Make World (http://makeworld.eu). After more than one year of use, we studied how students and teachers used this tool to propose and solve learning activities where computational thinking and STEAM skills are developed at the same time. This paper describes the main characteristics of Make World and analyses the use and piloting phase where more than 500 students of primary education have participated to measure the impact of Make World in their learning. The result of this analysis provides a better understanding of the difficulties students face when using a technological platform for STEAM and computational thinking education.