Best sensor for detecting crossing a line [COVID]

[PeterR]

Ok, understand.
IR is going to be better as Sprite says.
Saturation and reflection can be issues but Sprite's explains some simple mechanical solutions to avoid i.e. tube & filter.
Just thinking; pizo floor tiles? Not sure how that might be better but wonder....

[precipio]

https://create.arduino.cc/projecthub/pa ... _&offset=3