Detecting motion in a specific location

Projects General Guidance
1

I'm building a device that moves a laser across the floor for cat entertainment. I really like to have a feature to detect when the cat 'catches' the laser. So I thought of using a ultrasound sensor, but I'm not sure if I can measure across several meter/feet.

So the question is, how can I detect movement in a straight line? And which sensor can I use for that?

2

Isn't there a serious risk of the laser damaging the cat's sight?

...R

3

Well there are cat laser toys for sale everywhere, so I think it's not gonna be a problem, it's a very weak laser anyway

4

Cigarettes are on sale everywhere also.

...R