// Naoki Nishigawa
uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;

float cro( in vec2 a, in vec2 b ) { return a.x*b.y - a.y*b.x; }
float sdUnevenCapsule( in vec2 p, in vec2 pa, in vec2 pb, in float ra, in float rb ){
    p  -= pa;
    pb -= pa;
    float h = dot(pb,pb);
    vec2  q = vec2( dot(p,vec2(pb.y,-pb.x)), dot(p,pb) )/h;
    q.x = abs(q.x);
    float b = ra-rb;
    vec2  c = vec2(sqrt(h-b*b),b);
    float k = cro(c,q);
    float m = dot(c,q);
    float n = dot(q,q);

            if( k < 0.0 ) return sqrt(h*(n            )) - ra;
    else if( k > c.x ) return sqrt(h*(n+1.0-2.0*q.y)) - rb;
                        return m                       - ra;
}

float sdBox( in vec2 p, in vec2 b ){
    vec2 d = abs(p)-b;
    return length(max(d,0.0)) + min(max(d.x,d.y),0.0);
}

vec3 capsuleColor ( float d, vec3 b, vec3 c1, vec3 c2, float g ){
    return sign(d) < 0.0 ? mix(c1, c2, abs(d) * g) : b;
}

void main() {
    vec2 coord = gl_FragCoord.xy;
    float base_mask = 1.0;
    vec3 base_color = vec3(0.0);
    float d = 0.0;

    base_color = capsuleColor(
        sdUnevenCapsule(coord, vec2(0, 0.6), vec2(0, 0), 0.35, 0.34),
        base_color, vec3(1.0), vec3(1.0), 30.0);
    base_color = capsuleColor(
        sdUnevenCapsule(coord, vec2(0, 0.15), vec2(0, -0.2), 0.3, 0.37),
        base_color, vec3(1.0), vec3(1.0), 30.0);

    base_mask = 1.0;
    base_mask *= step(0.0, sdUnevenCapsule(coord, vec2(-0.095, -0.55), vec2(-0.15, -0.93), 0.03, 0.01));
    base_mask *= step(0.0, sdUnevenCapsule(coord, vec2(-0.05, -0.55), vec2(-0.05, -0.95), 0.03, 0.01));
    base_mask *= step(0.0, sdUnevenCapsule(coord, vec2(0.0, -0.55), vec2(0.0, -0.95), 0.03, 0.01));
    base_mask *= step(0.0, sdUnevenCapsule(coord, vec2(0.05, -0.55), vec2(0.05, -0.95), 0.03, 0.01));
    base_mask *= step(0.0, sdUnevenCapsule(coord, vec2(0.085, -0.55), vec2(0.20, -0.9), 0.03, 0.01));

    float a = -0.9, b = -0.3;
    float t = (clamp(coord.y, a, b) - a) / (b - a);
    float e = 1.0 - pow(1.0 - t, 3.0);
    base_color = base_mask > 0.0 ? base_color : mix(vec3(0.2, 0.2, 0.5), vec3(0.3, 0.9, 1.0), e);

    base_color = capsuleColor(
        sdBox(coord + vec2(0.0, 0.4), vec2(0.13, 0.2)),
        base_color, vec3(0.0, 0.5, 1.0), vec3(0.0, 0.5, 1.0), 1.0);
    base_color = capsuleColor(
        sdUnevenCapsule(coord, vec2(0, 0.61), vec2(0, -0.2), 0.24, 0.28),
        base_color, vec3(0.0, 0.5, 1.0), vec3(1.0, 0.2, 0.7), 3.0);

    base_mask = 1.0;
    base_mask *= step(0.0, sdUnevenCapsule(coord, vec2(-0.1, 0.6), vec2(-0.15, 0.75), 0.05, 0.03));
    base_mask *= step(0.0, sdUnevenCapsule(coord, vec2(0.1, 0.6), vec2(0.15, 0.75), 0.05, 0.03));
    base_color = base_mask > 0.0 ? base_color : vec3(1.0, 0.5, 0.2);
    colour_out = vec4(base_color, 1.0);
}