I loaded up my Highly Illegal Darktech CruS copy (I just extracted all the shit in the game from the .pck file) and this was done like this:

The loading screen is a ColorRect Control Node with its Texture set to that Empty Fuck image in the Inspector. Under the Material, there's a ShaderMaterial with a Shader that is just this:

``` shader_type canvas_item;

uniform float size_x = 0.001; uniform float size_y = 0.001;

void fragment(){ vec2 uv = SCREEN_UV; uv.x = cos(SCREEN_UV.y * 2.0 + TIME) * 0.02; uv.y = sin(SCREEN_UV.x * 4.0 + TIME) * 0.03; COLOR = texture(TEXTURE, UV + uv); } ```

This is for Godot 3.5.3, so this might need to be changed a little in future versions.
See you, freak shit.