First-year university students exhibit considerably different levels of proficiency, often lacking the necessary prerequisites to attend certain courses. This is especially true for mathematics courses. While motivation alone plays a role, by far the most significant challenge consists in harmonising the different (and often incompatible) backgrounds of the students. In response, universities have made various attempts to tackle this issue. Many institutions now offer intensive courses prior to academic entry or even complete introductory courses occupying the whole first term, whether in a classroom or (partially) online. Massive Open Online Courses (MOOCs), while relatively unknown until a few months ago, have brought about a real educational revolution. The MOOC is an educational model that brings online learning content to any person willing to participate. At Pompeu Fabra University (UPF) we were intrigued by this new educational paradigm and wondered whether it could be useful in filling the gap between high school and university. Therefore, we recently designed and implemented such a course: while remaining available to anyone, the course specifically targets our prospective students who in turn should tackle first-year linear algebra having acquired an adequate background. In this paper we describe the first MOOC launched by UPF, "Decoding Algebra". We provide an overview of its design, the technological means we used, our students' profile and the lessons from this experience. More importantly, by focusing on our incoming students, we examine whether MOOCs can be a good approach to level out the differences among first-year university students.