Rotation of a figure

Rotation of a group of points. Move original (blue) points or input coordinates at top left. Use green slider to change angle of rotation. Purple points show the rotation.
How do the x- and y-coordinates of each point change as you rotate 90 degrees? What about 180 degrees? If a figure is in quadrant II and is rotated 180 degrees, what quadrant will the rotated figure end up in?