Sure, here's a simple generative art game written in JavaScript, enclosed in script tags within a single HTML file:
When you open this HTML file in a web browser, it will display a canvas filled with generative art. The art consists of random shapes (circles or squares) with random colors, randomly positioned on the canvas.
Each time you refresh the page, a new set of art will be generated. You can even modify the code to add interactivity or different patterns as per your requirements.