I would really like to have a new set of LEDs come on as motion continues
To do what you want would take more then one PIR one can only tell if your moving but with 3 you could tell where you moved and if it was from right to left or left to right
That would let you light the spot you moved into. One can't do that.
But for the
but will be satisfied with all LEDs getting brighter with continued motion.
Just wait for trigger then count time it's on and let that update your PWM that controls your leds
Pir High counter started leds on 50% 1 second passes leds 60% then 70 80 90 100 if you stay for 5 seconds.