an akari puzzle.
First, note that we cannot place the light here, otherwise it’s impossible to light both squares marked with an X:
Therefore, we can eliminate these two squares:
From here, we can eliminate all these squares by using the 1s along the diagonal:
So the lights for the 2 are determined:
From here, we “rescue” the two red cells:
Now note that we either place lights on the blue cells or the red cell. However, we can’t use the blue cells because they light one another, therefore we must light the red cell (this is the aspirin-box technique):
From here, we can get the remaining lights by number requirements and rescues:
