HP = High Priority Queue
LP = Low Priority Queue
BL = Backlog
DONE = DONE

HP_CAPACITY  = 10
LP_CAPACITY  = 40
LEARNED_LIMIT = 30

Case 1: HP < (HP_CAPACITY/2)
1. move Math.min(LP, HP_CAPACITY/4) cards from LP to HP, fill remaining HP from BL
2. peek card from HP
3. if correct -> dequeue from HP
  a. if (correct - incorrect >= LEARNED_LIMIT) move to DONE
  b. else enqueue into LP
  else if incorrect -> dequeue from HP, enqueue into HP