From the last bit in that video I would suggest he is using two sensors, one on top and one on the bottom, and what I am thinking is that he is using the sensors to run a timed light sequence where the LED's light up sequentially as shown (either from the top or bottom depending on which sensor is tripped). The sequence runs for about 12 seconds from first LED fade-on to last LED fade-off. I think he did a small time study to determine what will be the slowest time that a person (being him) will walk up the stairs (or down), and merely used that as a time guide.
Then programmed the light array to fade-on each LED in sequence, pause roughly 3 seconds, and start fade-off the LED's from the first LED that was switched on.
Hope that makes sense...first time I ever put my hand into explaining a electronic sequence :drooling_face:
P.S. I will describe the sketch in words since I haven't ordered my gear yet.
Wait for sensor 1 & 2
if Sensor 1 = HIGH then sequence 1
if sensor 2 = HIGH then sequence 2
Sequence 1 & 2 is the same, the only difference is the order in which the LED's light up.
Fade on LED 1
Fade on LED 2
Fade on LED 12
Fade off LED 1
Fade off LED 2
Fade off LED 12
Sequence 2 will just be the reverse of sequence one.
That what I would do anyway to have the same thing practically and cheaply.