#version 300 es

#define PI 3.1415926
#define THETA 2. * PI

precision highp float;

uniform float iTime;
uniform vec2  iResolution;

uniform vec3 bg_color; //value=0,0,0
uniform vec3 fg_color; //value=1,1,1

uniform int enemies; //value=8, min=2, max=16, step=1
uniform float enemies_rotation_speed; //value=0.5, min=-10, max=10, step=0.001

uniform float level_time; //value=100, min=0, max=1000, step=1
uniform float level_radius; //value=0.6, min=0.1, max=1, step=0.001

vec2 q;

out vec4 fragColor;

bool circ(vec2 p, float r, float t){
    return length(q - p) >= r && length(q - p) < r + t;
}

// -1 - inner fill
// 0 - border
// 1 - outer
int circf(vec2 p, float r, float t){
    if(length(q - p) < r) return -1;
    if(length(q - p) >= r && length(q - p) < r + t) return 0;
    return 1;
}

void main() {
    // Screen coordinate (from [-aspect, -1] to [aspect, 1])
    q   = (2. * gl_FragCoord.xy - iResolution) / iResolution.y;

    vec3 fill_color = mix(fg_color, bg_color, 0.75);

    vec4 col = vec4(bg_color, 1.);
    
    //completion
    float r = min(iTime / level_time * level_radius, level_radius);
    col = circ(vec2(0., 0.), 0., r) ? vec4(fill_color, 1.) : col;
    col = circ(vec2(0., 0.), r, 0.005) ? vec4(fg_color, 1.) : col;
    
    //ring
    col = circ(vec2(0., 0.), level_radius, 0.02) ? vec4(fg_color, 1.) : col;
    
    //rings
    for(float i = level_radius + mod(iTime / 5., .2); i < 2.2 + mod(iTime / 5., .2); i += .2){
        col = circ(vec2(0., 0.), i, 0.01) ? vec4(fg_color, 1.) : col;
    }
    
    //outer things
    for(float a = -iTime * enemies_rotation_speed; a < THETA + -iTime * enemies_rotation_speed; a += THETA / float(enemies)){
        vec2 p = vec2(cos(a), sin(a)) * (level_radius + 0.1 + 0.01);
        int c = circf(p, 0.1, 0.01);
        
        if(c == 0) col = vec4(fg_color, 1.);
        else if(c == -1) col = vec4(1., 1., 1., 1.);
    }
    
    //player
    int c = circf(vec2(0., 0.), 0.03, 0.0025);
    if(c == 0) col = vec4(fg_color, 1.);
    else if(c == -1) col = vec4(1., 1., 1., 1.);
    col = circ(vec2(0., 0.), 0.025, 0.005) ? vec4(fg_color, 1.) : col;

    // Output
    fragColor = col;
}