Concentrate!

We all think we're observant - but are we really?
You are shown a screen containing random characters which you must memorise. The screen clears and you’re asked a question on what you saw. How hard can that be?
There are 20 screens on each level, each one has an additional character and an additional second to study.
Each level adds an extra question type. You start with three lives. If you get a question wrong you lose a life and restart the level. If you lose all your lives you restart the entire game.
Concentrate!