Please consider using http://lygia.xyz instead of copy/pasting this functions. It expand suport for voronoi, voronoise, fbm, noise, worley, noise, derivatives and much more, through simple file dependencies. Take a look to https://github.com/patriciogonzalezvivo/lygia/tree/main/generative
float rand(float n){return fract(sin(n) * 43758.5453123);}
float noise(float p){
float fl = floor(p);
float fc = fract(p);