I tried it on a mac with FF 60, also tried it with your resolution of 1366 x 768, no sign of the issue. It might be a race condition or logic error leftover from story mode using click to go through the dialogues, in which case 'quick game' mode should work after refreshing the page.
Ah, no joy I'm afraid. I tried a couple of browsers but, honestly, it's most likely my computer being outdated. It's telling that I picked up a book while booting it up. Windows 7 is pretty old by now.
Thanks anyway for trying, it is a neat game.