I have found that in every lesson, if I accidently press backspace, and I have error correction set to "Use backspace" I have to press backspace again to correct. This might not be a problem for qwerty users, but on Colemak it is easy to hit backspace accidently. While it isn't a major issue regardless, it seems a bit off.

Thank you very much for your bug report! You noticed an error, we never noticed before. That's great. We will change it as soon as possible.

All the best from Berlin,
Your Tipp10 Team