This is probably on purpose so tell me if I'm wrong, but are you stuck on horizontal mode if you're on mobile? I'm like 99% sure you could play it vertical but you can't anymore :(
I think it's a browser thing on mobile. I was playing on Google granted it was the go version and it wasn't horizontal but vertical but when I played on chrome it would default to a horizontal display with no way of adjusting to the vertical/normal display
