HTML5 'hidden' attribute and assistive technologies

Hello,

I would like to use this responsive menu on a site I am building: https://codepen.io/Kilian/pen/yLBQBpK

I can see that when the viewport is over 40rem wide, the menu is visible horizontally. However, the ul#menu still has the 'hidden' attribute applied, although it is visible.

Is there any problem with this behaviour? Will a screen reader anounce the menu although it has the hidden attribute?

Thank you.

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Bernat Lleonart