Just stumbled upon this when perusing the backlog for handmade hero as I'm want to do!
It looks like your browser has held on to an old stylesheet. I can't replicate the problem, but I recognise the symptoms. We're still ironing out some cache busting issues when we update the stylesheet, but other than that it should sort itself out.
You could try and change the theme from light to dark, see if you still have the issue, then switch back again. That may be enough to cause the browser to flush its cached old version.
Making cache busting more robust is on our todo list, so if you see this at all (and most people probably won't), it's temporary.