While this algorithm is very simple it doesn't seem to take into account critical periods in memory formation. Just choosing which card to show next is only ha

While this algorithm is very simple it doesn't seem to take into account critical periods in memory formation. Just choosing which card to show next is only half the battle. If you're learning X cards you need to review all X within the first hour, then the next period of 24-48 hours, etc. The forgetting curve which underlies spaced repetition has some biological tipping points (did you sleep between your last session and this one) which are not easily approximated. I strongly support software like this, but would prefer a complex accurate system, to a simple elegant one.