First and foremost, thank you for this! Have been looking forward to this with much anticipation, and am super having fun learning Czech!

In the Masculine section, there are exercises where there is a picture, and one must enter the word for the object in the picture. The "Check" button remains greyed-out, so the answer cannot be submitted. The "Skip" button is active. Below is the link from the address bar where this behavior occurred.

https://www.duolingo.com/skill/cs/Masculine/1

Thanks again for putting this together :-)