In 2018 we worked one year in a small team of circa ten people to develop Harp.gl. It is a 3D map technology that runs in the browser, developed using Three.js and Typescript. During our time there, we worked on the mouse-picking functionality using raycasting, on the rendering of the sky, on how to render the lines that delimit the borders of a country and on preparing the examples that show how to integrate React with the Here Maps Javascript API.