"Your learning progress" graph - anyone know how that works?

It doesn't seem obviously related to any factors I can think of (completion speed, accuracy, etc.). It just gave me a near-perfect score for an honestly pretty dismal run, so I was just wondering. Anyone have an idea?

Hi Empatheia, the learning progress graph and scores work like this.

Every time you get a question correct you get 1 point for that question up to a maximum of 6 points (which is a perfect score).

Each time you answer a question incorrectly you lose 4 points for that question, though you can't go below 0.

You are more likely to be asked questions with a low score.  This way you end up practicing more on the questions that you struggle with.

Every time you finish a game, you can see your current score for each question that you answered in the game.

Its a fairly simple system I know ... but its worked well for me