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@@ -74,7 +74,7 @@ Our goal is to evolve a *breaker*. Deliberately we will use a very few knowledge
   * A feedback $`\langle N, 0 \rangle`$ means that they guessed the code
   * The fact that the feedback is deterministic. In particular, this means that it is useless to make the same guess more than once during a game, because this will not bring any new information.
 
-Note that the breakers do not know the meaning of the feedbacks (except of the winning one) and hence they can play only a trial and error strategies.
+Note that the breakers do not know the meaning of the feedbacks (except of the winning one) and hence they can play only trial and error strategies.
 
 ## Breaker representation
 
@@ -82,6 +82,28 @@ We will represent a breaker as a rooted tree. Each node of the tree is a guess.
 
 ![example of a (3, 3)-game decision tree](example_tree_3_3.png)
 
+Nodes where the breaker gets the winning feedback are drawn with bright colors. We will call them *terminal nodes*.
+
+The first guess of the breaker is the root node. After getting a feedback, it goes down to the corresponding child node and emits the next guess. It stops when it gets the winning feedback. So for a given code $c$, the game is described by a path starting at the root, following the corresponding feedback edges at each node and finishing at $c$. We will call this path *a game path* for $c$.
+
+---
+
+**Example.** Let the secret code be RRR. The first guess is BRG and the breaker gets feedback $`\langle 1, 0 \rangle`$. The second guess will be GBB with feedback $`\langle 0, 0 \rangle`$. This feedback leads to a guess RRR and a winning feedback.
+
+---
+
+Of course, not all trees with the above structure are valid players. To represent a valid breaker, a tree must contain a game path for each possible code.
+
+---
+
+**Example** The following tree does not represent a valid breaker:
+
+![Example of invalid  tree](example_invalid_tree.png)
+
+To show this, consider again the `RRR` secret code. The first guess is BRG with feedback $`1, 0`$. Going down on the corresponding branch, the second guess is BBB with feedback $`\langle 0, 0 \rangle`$. Then the third guess is GGG and the feedback is again $`\langle 0, 0 \rangle`$. Now the breaker does not know how to play because the node GGG does not have a subtree labeled $`\langle 0, 0 \rangle`$.
+
+---
+
 
 
 # References