A small and intentionally poorly-performant demo used for investigating some behavior in the Performance panel in DevTools.
On page load, a grid of 16,320 square divs is drawn to the screen: half are black, half are pink. Pressing the left and right arrow keys recolors these "pixels" by adding and removing CSS classes four columns at a time. This causes lots of screen repainting.
No local server needed; just open index.html in the browser straight away.
