Learn how to use Uniform variables. Uniform variables, or simply *uniforms* are the variables that carry information equally accessible from all of the threads of your shader. The [GSLS editor](http://editor.thebookofshaders.com/) has three uniforms set up for you.

```glsl
uniform vec2 u_resolution; // Canvas size (width,height)
uniform vec2 u_mouse;      // mouse position in screen pixels
uniform float u_time;	  // Time in seconds since load
```