Three computer fans 40x40mm carry a mirror under a small angle with the motor shaft. The beam of a 5 volt laser pen diode hits the first mirror under an angle of 45 degrees. That beam is reflected twice by the two other mirrors. The beam escapes through an opening and projects Lissajous patterns at the wall or ceiling. The speed of the three fans is individually controlled by three 555 PWM circuits allowing to generate math art.
Try to hit the mirrors in the middle. An effective way to adjust is changing the distance of the mirror to the motor by applying some layers of double sided adhesive foam tape between fan and mirror. Or change the thickness of the disk. For that reason the Open SCAD file of the disk is attached.