I've complete a linear cryptanalysis attack towards simple a toy SPN cipher, I feel very veryyyyy happy!

Steps to follow to finish my attack

1. Generate LAT(linear Approximation Table) of SBOX, if there are many SBOXs, generate LATs for each of SBOX.
2. Find path to construct a good path.(Good for me, I'll explain it later.)
3. Get enough plainttext-cipher pairs, for a bias of $\varepsilon$, a reasonable amount of $\frac{1}{\varepsilon^2}$ is required, the more, the better. But too much does not make much sense.
4. For your constructed path, try to recover keys by following instruction of tutorial.
5. Repeat step 2-4 until you get subkey of last round.
6. Repeat step 1-5 until you get all subkeys except first XOR.
7. Use subkeys to recover first XOR key by reverse encryption process and known plaintext.

I'll show a detailed example by a post, just wait.;D