Mobile app minor issue and feedback

I have noticed that dark mode essentially flips the colours. This also applies to pictures, diagrams etc causing photos to look like a negative. The dark mode should ignore photos. I also have a suggestion regarding the colour of the lesson icon, currently they are blue and get a tick mark once completed. I personally find it a little hard to see on mobile. Perhaps yellow for incomplete lessons and blue for finished lessons would be better? Or any other colour to easily see what I've completed? Many thanks to everyone creating this amazing content!