Color Vignette with some additional parameters (webGL and webGPU).
I guess this question is not about the effect but about Construct 3 itself.
You cannot add to effect parameters like this and also you cannot get the current value of an effect parameter (I have written suggestions for this to Scirra, but it has not been added)
I have a similar functionality in my game, I do it by having a strength variable, I add and subtract from that variable and set the parameter to that variable.
thanks for reply, i think i should set strenght to 25 and wait 0.1s and set again to 0 to blink red hurt effect or use your solution to use variable. thanks