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1: The shader_type is of canvas_item which means it is a 2D Shader
3: Declare a variable called speed, set its value to 0.5.
uniform means this variable can be adjusted from outside the shader, like in the Godot editor or by
a script.
5: The vertex function affects the position of each vertex in the object
6: UV represents the coordinates on the texture (where (0,0) is the top left).
TIME is a built-in variable that changes as time progresses.
7: By adding TIME * speed to UV.x and UV.y, it offsets the texture coordinates over time,
causing the texture to appear as if it’s scrolling diagonally.
So, this shader smoothly moves the texture diagonally across the object at a rate controlled by speed. The larger the speed, the faster the texture scrolls.