juliet/shaders/world_vs.glsl

#version 120
// input
attribute vec2 vp;
uniform vec2 vp_offset;
uniform vec2 size;
// output
varying vec2 frag;

void main() {
  gl_Position = vec4(vp+vp_offset, 0.5, 1.0);
  frag = vp/size;
}