IT-CESENATICO 2012 Problem 5

$ABCD$ is a square. Describe the locus of points $P$ , different from $A, B, C, D$ , on that plane for which $\widehat{APB}+\widehat{CPD}=180^\circ$

Dataset text AI-MO AoPS. Quoted with source.

Solutions

No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.