Simple constraint

If p₁ follows p₀, then p₁ gets its coordinates from the following set of equations:

$d_{p}=p0_{x}-p1_{x}$

$d_{y}=p0_{y}-p1_{y}$

$l_{1}=d_{x}^{2}+d_{y}^{2}$

$p_{1}dx=d_{x}/l_{1}*r-d_{x}$

$p_{1}dy=d_{y}/l_{1}*r-d_{y}$

, and finally

$p_{1}x+=p_{1}dx$

$p_{1}y+=p_{1}dy$