Sure! Here's a sample implementation of a game builder garage Splatoon game in a single HTML file, using JavaScript and enclosed in script tags:
This simple game allows you to control a square player using touch input on your smartphone. The player moves according to your finger's position on the screen. The player's color is set to red in this example.
You can save this code in a .html file and open it in a web browser on your Nintendo Switch using the built-in web browser. Enjoy playing your custom Splatoon-themed game in Game Builder Garage!