Assuming you already have node installed on your computer. If not, you can use homebrew to install node
brew install node
Theming origin requires help from node-sass, gulp and bower, so we need to install them first.
sudo npm install --global gulp node-sass bower
These tools should be install globally, so we include a flag --global in the command.
For the first time cloning origin theme, you'll need to install node package required for the workflow:
$ cd [drupal]/themes/custom/origin
$ npm install
🚨 The current configuration is set up to work with local development only. Local hostname must match variable found in GulpConfig.js
ie: I use MAMP set up with vhost name d8boilerplate.pantheon, so in GulpConfig.js, hostname must say the same d8boilerplate.pantheon.
To start working on theming:
$ cd [drupal]/themes/custom/origin
$ gulp
Development website will be opened automatically on your default browser.