#version 300 es

precision mediump float;

in vec2 fragTexCoord;
in vec4 fragColor;
out vec4 finalColor;

uniform vec3 color;
vec2 offset = vec2(1.0, 1.0);

float start_transparency = 0.40f;
float sun_radius = 0.6f;
float sun_end = 1.0f;

void main()
{
    offset.x -= fragTexCoord.x * 2.0;
    offset.y -= fragTexCoord.y * 2.0;
    float radius = length(offset);

    if(radius < sun_radius){
        finalColor = vec4(color, 1.0);
    }else if(radius < sun_end){
        float gradient = radius;
        gradient -= sun_radius;
        gradient = gradient / 0.4f * start_transparency;
        finalColor = vec4(color, start_transparency - gradient);
    }else{
        finalColor = vec4(color, 0.0);
    }
}