Noise-based lightning shader like in Zelda?

So I am trying to follow this in code and gettiing nowhere…

This is my code

			float4 frag(v2f i) : SV_Target
		{
			float4 col = _Color;
			fixed4 tex = tex2D(_Noise, i.uv);

			float noise = tex.r;

			// how is this mean to animate? The node base images don't show what it lerps between and over what time
			float lerpTime = (sin(_Time * 10) + 1) * .5;
			noise = lerp(noise, noise *2, lerpTime);

			// this returns really harsh, cut out pixelated values
			_WidthParam = .25;
			float width = _WidthParam * fwidth(noise);
			float edge0 = noise - width;
			float edge1 = noise + width;

			float arc= smoothstep(edge0, edge1, noise);

			col *= arc;

			return col;
		}

and this is my results:

any help would be great thanks!