impact shader

tutorial followed from here:

Shader code

shader_type canvas_item;

uniform vec2 center;
uniform float force;
uniform float size;
uniform float thickness;

void fragment(){
	float ratio = SCREEN_PIXEL_SIZE.x / SCREEN_PIXEL_SIZE.y;
	vec2 scaledUV = (SCREEN_UV - vec2(0.5,0.0)) / vec2(ratio, 1) + vec2(0.5,0.0);
	float mask = (1.0 - smoothstep(size-0.1,size, length(scaledUV - center))) * 
	smoothstep(size-thickness-0.1,size-thickness, length(scaledUV - center));
	vec2 disp = normalize(scaledUV - center) * force * mask;
	COLOR = texture(SCREEN_TEXTURE,SCREEN_UV - disp);
//	COLOR.rgb = vec3(mask);
	
}