Very good update.
Being able to adjust visuals really helps on the web version. It runs quite well for me now if I disable blood, even with a horde of 100+ zombies.
I confirm that the UI works fine too.
Being able to buy zombies helps with the fact that it's hard to get a huge horde, but at the current cost, it can be spammed to overcome any enemy once you have a good income. Maybe the prices could scale with your horde size and/or current zone?
I tried restarting from a fresh save and the tutorial works well. Although, new zombie types are introduced quite early when you're still far from being able to afford any. It gives something to look forward to, so maybe that's fine but I think I might want to get the infection upgrades first.
Anyway, very good work :)