As we can see, in this game every level has exactly two outgoing and two incoming transitions, so we will call it a balanced 12-level game with two outputs. For example, from level 1 the player can move to levels 2 and 4, while level 1 itself can be reached from levels 10 and 12. The transitions are shown in different colors purely for clarity, making it easy to count how many choices the player is offered at each step (the red and blue arrows even create an association with the pills from The Matrix).
The difficulty in creating balanced maps is not in assigning the required number of outgoing arrows to each level, but in ensuring that, in the end, every level also receives the same number of incoming arrows. In the next map, for example, each level has two outgoing arrows, but the numbers of incoming arrows are not the same. In particular, levels 4 and 6 each have three incoming arrows, while level 5 has none at all. As a result, level 5 cannot be reached from any other level, meaning that the only way to include it in the game is to make it the starting level.