precision mediump float;
uniform float alpha;
#if defined(DEBUG_FLAGS)
uniform float tint;
#endif
uniform vec2 size;
varying vec2 v_coords;

uniform vec3 color;
uniform float thickness;
uniform float radius;

float rounded_box(vec2 center, vec2 size, float radius) {
    return length(max(abs(center) - size + radius, 0.0)) - radius;
}

void main() {
    vec2 center = size / 2.0 - vec2(0.5);
    vec2 location = v_coords * size;
    vec4 mix_color;

    float distance = rounded_box(location - center, size / 2.0 - vec2(thickness / 2.0), radius);
    float smoothedAlpha = 1.0 - smoothstep(0.0, 2.0, abs(distance) - (thickness / 2.0));
    
    mix_color = mix(vec4(0.0, 0.0, 0.0, 0.0), vec4(color, alpha), smoothedAlpha);
    
#if defined(DEBUG_FLAGS)
    if (tint == 1.0)
        mix_color = vec4(0.0, 0.3, 0.0, 0.2) + mix_color * 0.8;
#endif

    gl_FragColor = mix_color;
}