It searches for the brightest light source like the sun.
Step 1: How it works
I'd made a sensor of 4 LDRs with sheets between them
The withe stips are the LDRs
the four LDRs get the same amount of light on them.
Example1 when the light is left on top:
right-top, right-down, left-down are in the shadow
and left-top get the most light
Example2 when the light is on top
left and right down are in the shadow and top is in the light