Arrows

Background

This puzzle was invented by Erich Friedmann.

An unsolved puzzle is a rectangular grid. In each cell is a number and an arrow.

The goal is to color the arrows according to the rules.

The solved grid must satisfy the following conditions:

A white arrow points to N white arrows, where N is the number inside the arrow.

A black arrow points to some number of white arrows other than N.

Scheinwerfer; Spotlight