SM4T: Scratch MOOC for Teens" represents a novel joint initiative developed by Universidad ORT Uruguay and Plan CEIBAL. CEIBAL is a governmental project of Uruguay which includes, among other projects, the distribution of free laptops and free access to Internet to students and teachers of primary and secondary public schools. We designed and implemented a Massive Open Online Course (MOOC), oriented to 1000+ teenagers students. This MOOC aims to promote the development of procedural thinking and problem-solving skills through learning the basics of computer programming building applications (videogames) using Scratch, a programming language designed for young people, developed by MIT's Media Lab. To be able to attend this course, no previous knowledge or background on computer programming, or use of the Scratch tool is required. The course is entirely implemented using Plan CEIBAL's CREA platform, offered to students through CEIBAL's computers via Internet. The first trial was conducted from October to November, 2013. In this article we present the characteristics of our MOOC in their context, the detailed course description, initial results, good practices, lessons learned, and some conclusions.