Sensitive to light and room for improvement!

Neutral:
Partially difficult questions, even on the lowest age group! Whether that is good or bad, everyone should judge for themselves.

Negatives:
App does not run on any version of Android. Eg problems with ZTE Skate / Medion. So better to install before buying!
Quite susceptible to uneven lighting. Disturbing shadows or additional light.
Partially a (correct) answer is not recognized or asked a question incorrectly. This high frustration potential.
Legal computationally intensive. The Nexus 4 used crashes after about 25mins, as heat problems caused by the continuous operation of the processor. Use of flash enhances this effect.

Conclusion:
Quite nice, but still too many problems!