See the demo page

This library calculates the visible area in a closed room from a central point. The calculations are exact, to the extent that floating point arithmetic allows.

The inspiration comes from the soldiers' view field in the Commandos game series.

• You need to cover the center with walls all-around to get 360 degrees of shadows
• The wall segments cannot overlap, or touch each other in the middle, only end-to-end overlaps are allowed