As a tech guy that knows design is important this is great. I'd love to see themes where the headers are a certain font, body another, etc. Picking one font is hard enough but picking multiple fonts that go together is much harder.
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Good for non dev types to quickly test a different font on their site without screwing around with code, great first iteration, appears to lack ability to use different fonts for different parts of the site (most headlines are different to body).
Like the browser extensions. Not sure how they will monetise but it is really useful and does solve a problem.
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