That’s surprising, because I use firefox, and it works for me here, too. The only difference is that on itch.io the game is embedded on a frame, so one needs to click on the frame (but outside the canvas, so on the light background) to focus it. At least, that’s how it works on firefox for me, but maybe not on all versions/configurations? Maybe try shift+click there or something, to ensure the click is not intercepted by anything?
Works with firefox on my friend's computer too. Not sure what's wrong with mine. Couldn't get it to work but it works fine on the other site so it's not too big a problem. Game loads but doesn't repond to mouse or keyboard, including with shift click. Right clicking lets me open up a picture of the title screen as an image.