Fragment Shader played in Reverse

Hey!This is WebGl!I have this fragment shader that I found on shadertoy.com, and now I'm going to implement it via three.js. My issue is that I would really want to be able to go control the "time" of the shader. So that I can let it "play" and then "reverse" the effect to get it back to the starting point. It will also be interactive so it's not a question of an animation.What would be the best way to do this? I'm new when it comes to fragment shaders.Here's the shadertoy effect:https://www.shadertoy.com/view/ldcGDXWould really appreciate an answer, thank you!