This is the code used at https://merrychristmasandahappynewyear.com/ .
The gist of it is that it takes the sentence "merry christmas and a happy new year" and splits it into words and letters. Each letter is represented by a template files in public/static-assets/grid-templates which is parsed in to an array. The array is then used to create HTML code to which some CSS is applied in order to create a grid.