The middle game is the gray zone between opening and end game. It can be seen as preparation for the end game. It’s hard to give general rules how to play the middle game, because a lot depends on the situation. Sometimes it can be good to play fast and to force the opponent to move some pits, and sometimes it’s better to play slow and wait for the opponent to play one of his big pits. Nontheless we’ve got some advice grouped in two categories: tuzdyk value and collecting balls.
The value of a tuzdyk depends a lot of the situation. It is estimated to be usually between 15 and 30 balls. There are some exceptions, for example making a tuzdyk on 8 towards the very end usually doesn’t help much (losing too many moves by doing so). Here is an approximation of the tuzdyk values by top player Serik Aktayev:
Too many big pits can become an obstacle, therefore they should be played on time. It’s often best to play them when you can make a tuzdyk or a capture on the other side. If this is not possible then it can be good to play them when their size is about 18, losing the least moves, however if your pits are already big, then it can be better to wait longer, especially if the big pile is to the left (for example on 2). It’s usually best to collect balls right in front of the opponent’s tuzdyk or on 9. If you collect 20 balls on 9 and 1 on the other side is free, then you can play 91 and capture two balls at 1 right away. Sometimes it’s also good to collect at 2. Rarely it can be good to collect at another spot, but keep in mind big piles at 1 can always be forced and collecting on 8 loses a lot of moves compared to collecting on 9.