It feels like you are a few years late to the party but: welcome and good luck with the app!
Good to see you are adding block development for STEM classes, something that has been missing for a while now.
I did a quick test flight on an ancient Pixel 3, here is my 100% biased feedback:
Positives:
You guys obviously have much better graphics & design skills than I do ;-)
The intro & tutorials are really nice and super useful - but please make sure
tello moves into the right direction on stick moves
Negatives:
The live feed & recorded video are broken on the Pixel 3. Video shows upper left corner, using 15-20% of the screen area. The other 80% of the screen are green.
Pictures are snapshots taken from that broken video. Apart from the green problem this always gives super low photo quality. That just plain sucks given that
Tello has a great still camera.
Stick controls feel strange. It seems to be mutually exclusive, so its either pitch / yaw / throttle / roll but no mix of these, and the sticks don't have a proportional feel. Or maybe my thumbs are too thick.
The next issue made me delete the app, sorry:
Tello kept moving after sticks were released until it crashed into a wall. You should review your control loop and add watchdogs.