#define PI 3.14159265359
  
  //Anti-aliased coordinate system grid
  float coordinateGrid(vec2 coords) {
    vec3 axesColor = vec3(0.0, 0.0, 1.0);
    float axesThickness = 0.015;
    
    vec3 gridColor = vec3(0.5);
    float gridThickness = 0.008;
    
    float retrn = 0.0; // What is this returning?
    
    //Draw grid lines
    const float tickWidth = 0.1;
    for(float i=-2.0; i<2.0; i+=tickWidth) {
      // "i" is the line coordinate.
      retrn += 1.0 - smoothstep(0.0, gridThickness, abs(coords.x - i));
      retrn += 1.0 - smoothstep(0.0, gridThickness, abs(coords.y - i));
    }
    
    //Draw the axes
    retrn += 1.0 - smoothstep(0.001, 0.015, abs(coords.x));
    retrn += 1.0 - smoothstep(0.001, 0.015, abs(coords.y));
    
    return retrn;
  }

//returns 1.0 if inside circle
float circle(vec2 coords, vec2 center, float radius) {
  	float antiAliasTolerance = 0.005;
	return 1.0 - smoothstep(radius - antiAliasTolerance, radius + antiAliasTolerance, length(coords - center));
}

//returns 1.0 if inside rectangle
float rectangle(vec2 r, vec2 topLeft, vec2 bottomRight) {
	float ret;
	float d = 0.005;
	ret = smoothstep(topLeft.x-d, topLeft.x+d, r.x);
	ret *= smoothstep(topLeft.y-d, topLeft.y+d, r.y);
	ret *= 1.0 - smoothstep(bottomRight.y-d, bottomRight.y+d, r.y);
	ret *= 1.0 - smoothstep(bottomRight.x-d, bottomRight.x+d, r.x);
	return ret;
}

void main(){
  vec2 p = vec2(gl_FragCoord.xy / resolution.xy);
  vec2 r = (vec2(gl_FragCoord.xy - 0.5*resolution.xy)*2.0)/resolution.y;
  float xMax = resolution.x / resolution.y;
  
  vec3 bgCol = vec3(1.0);
  vec3 col1 = vec3(0.216, 0.471, 0.698); //blue
  vec3 col2 = vec3(1.00, 0.329, 0.298); //yellow
  vec3 col3 = vec3(0.867, 0.910, 0.247); //red
  
  vec3 retrn = bgCol;
  // --------------------------------
  // --------------------------------
  
 
  
  
  // --------------------------------
  // --------------------------------
  vec3 pixel = retrn;
  gl_FragColor = vec4(pixel, 1.0);
}