Create a rule that runs once (During an initialization phase)
do:
System.Windows.Forms.Cursor.Hide
Speaking of which...
BlueMonk: Maybe there should be a simple way to define rules that always run exactly once (per game/per level/per sprite/whatever). Rather than surrounding it in an if (initialized) block in the main code, have a separate area for rules that run during the constructor, or something? It's a very common use case, and while there is already a way to do it, it could be simpler and more efficient.