Panasonic Inverter microwaves vary the power intensity. You can also punch in multiple heating stages in sequence. For instance: 30 seconds at level 4 followed by 20 seconds at power 8 and etc etc.

Please tell me I’m not the only one that can see the plexiglass sheet in front of him?

Definitely not an art piece. This is done simply using a ASCII video output plugin in VLC or Mplayer (in linux).