How do a smooth transition of grayscale in my game?

HELLO! How can I make the transition of my game from a color scale to a grayscale but make it slow, so that little by little my screen changes to gray smoothly and not in such an aggressive way. I am already using the grayscale effect but I want it to activate slowly.

i need a capx please

Simply change the effect parameter from 0 to 100 over time.

| Global number p‎ = 0

+ System: Every tick

-> System: Set p to min(p+20×dt, 100)

-> System: Set layout effect "Grayscale" parameter 0 to p

.

Another option is to use Tween behavior. Start a value tween on some object from 0 to 100. While this tween is running, set effect parameter to Object.Tween.value("tag")