Google's Blockly is a library that adds a visual code editor to web and mobile apps. Sugarcube is a modified version of it for coffee engine, please note that this is only the blockly component of sugarcube, the rest is in the main Coffee-Engine repository.
More specifically Blockly version 10.4.2
To build run npm install and then npm run start in your console. It should load you into a blockly playground.
To build the minified version run npm run minify.