The @ symbol could easily be confused with the copyright symbol with the current design. Especially at smaller sizes, it looks a bit like a 'c' in an ellipse.

While the copyright symbol is obviously a copyright symbol, the @ symbol is not obviously an @ symbol.
Separating the tail of the 'a' from the outline should eliminate any potential confusion, such as:

Thanks for the feedback! The core problem is that both the @ and copyright symbol have been designed to have maximum internal space. I think that in context they're fairly straightforward to tell apart, but I'll leave this open so that if other people have issues with this then we can look to address it.
The copyright and registered symbols could be filled circles with a C or R reversed out.
The At symbol, could also terminate it's curved tail to the left side, rather than the bottom
Hmm. I'll have to do some experiments. Thanks!
Hmm. I'll have to do some experiments. Thanks!

What about connecting the 'a' slightly with the circle at the top, and let the tail stop slightly sooner?

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What about connecting the 'a' slightly with the circle at the top, and let the tail stop slightly sooner?