Greetings. I am bad at expressing longer thoughts, so I will be frugal with my words. Please do not perceive it in a negative way.
I find the multiple levels of correct answers very distracting. I would also rather sacrifice some efficiency to maximize the guarantee of remembering the material. With that in mind, I came up with my own scheduling system.
The repetition intervals would increase by one day with each strong recall; and decrease by one day with each weak recall, until value of one day is reached. Another rule is that the odd-counted entries in the current queue would have the interval length additionally decreased by one day in order to fuzz out groupings of similar cards. Initial interval would be set to two or three days depending on this rule.
Overall, there is no distinction of learning or recall phase. If the material is difficult to learn, the algorithm will quickly decrease the interval to one day and keep it there until the information is remembered successfully. On the other hand, if the material is easy to acquire, the interval will grow indefinitely, yet slowly. At any point, if the card is remembered weakly, the single-day decrease of the interval allows to strengthen this memory without going to directly to zero. There could be cases of cards which stay at a particular interval range due to their difficulty and that would be fine, too.
I have no programming skills and I do not know any programmer I could trust with this project. I run a self-employed business, so it would be easy to pay you with an invoice. The only questions are whether you are interested in implementing my scheduler and for how much money? If it is not obvious, let me add that I am not asking to replace the existing scheduler, but to have two of them available as options to choose from.
Best Regards,
Marek Paśnikowski from Poland