#version 330 core
out vec4 FragColor;

varying vec2 val;

void main() {
    float radius  = 1.0f;
    float radius2 = 0.5f;
    float smoothing = 0.005f;
    float dist = sqrt(dot(val,val));

    if (dist > radius || dist < radius2) {
        discard;
    }
    float sm  = smoothstep(radius,  radius  - smoothing, dist);
    float sm2 = smoothstep(radius2, radius2 + smoothing, dist);
    float alpha = sm * sm2;
    FragColor = vec4(1.0, 0.0, 0.0, alpha);
}