Pushing blocks all the way to C++

The BBC micro:bit project aims to teach programming to every 11 to 12-year-old in the UK, through the means of a programmable device half the size of a credit card. The device will be freely handed out to every student. Microsoft's TouchDevelop programming environment was picked to provide the programming experience for kids; we retrofitted the website for the micro:bit. TouchDevelop remains a complex beast: in order to make it easier for 7th graders to program, we added an alternative, visual code editor based on Google's Blockly [1]. This paper is an experience report about the various challenges we met when trying, at one end, to expose a visual Blocks-based programming model, while at the other end generating C++ for the device.