What secret code is hidden in this masyu puzzle?
Note: The regions marked with x are not to be drawn
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The X's scattered all over the board makes it a rather dull and mechanical puzzle, and still there is an ambiguity at the lower left corner:
How to get to this point:
Observe that the X's make the entire cell unusable, and therefore they act like the outer boundary for white/black pearls nearby. Specifically, if a white pearl is adjacent to an X, it means the line should pass straight through it in a specific way (e.g. horizontally if X is right above or below it). If a black pearl is adjacent to/one cell away from X, the line should extend from it two units in the opposite direction. Once this step is complete, proceed with usual single-loop deductions: avoid making a closed loop too early or making a dead end.
Assuming the edge goes straight vertically so it looks like this:
then the secret code is
3564, reading the digits horizontally. Note that the digit shapes overlap a little bit.