module StraightSkeleton::Node

def project(travel)
  det = normals.inject(&:cross) if normals.all?
  case
  when det&.nonzero?
    x = normals.map { |normal| travel - @travel + normal.dot(point) }
    (normals[0].perp * x[1] - normals[1].perp * x[0]) / det
  when normals[0] then normals[0] * (travel - @travel) + point
  when normals[1] then normals[1] * (travel - @travel) + point
  end
end