Ooh, that's strange. Doesn't look like that on my end at all.
Ah! I solved the mystery... I was playing it on my 4K monitor, which is set to the windows default 150% scaling. If I play it on my 1080p monitor, it looks correct.
Thanks for figuring that one out! If I scale the page it does the same thing for me too. Hopefully it'll be an easy fix!