Below in example sentence
But as a shortcut, you might notice that levels 8 through 11 are colored identically to 1 through 4. Since a level’s color is determined by the levels 1, 3, and 4 stories below it, this means that level 12 will be the same color as level 5, 13 will match 6, 14 will match 7, and so on, In particular, the losing levels will always be multiple of 7, and two greater than multiples of 7. Now, from your original starting level of 25, you have to make sure your opponent starts on a losing level every single turn— if NIM starts on a winning level even once, it’s game over for you.