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precision highp float;

uniform float time;

uniform vec2 resolution;

uniform sampler2D texture;

#define iGlobalTime time

#define iTime time

#define iResolution resolution.xy

mat2 mm2(in float a){float c = cos(a), s = sin(a);return mat2(c,s,-s,c);}

mat2 m2 = mat2(0.0, 0.29552, -0.0, 0.0);

float tri(in float x){return clamp(abs(fract(x)-.0),0.00,0.49);}

vec2 tri2(in vec2 p){return vec2(tri(p.x)+tri(p.y),tri(p.y+tri(p.x)));}

float triNoise2d(in vec2 p, float spd)

{

    float z=1.8;

    float z2=2.5;

    float rz = 0.;

    p *= mm2(p.x*0.06);

    vec2 bp = p;

    for (float i=0.; i<5.; i++ )

    {

        vec2 dg = tri2(bp*1.85)*.75;

        dg *= mm2(time * 10.*spd);

        p -= dg/z2;

        bp *= 1.3;

        z2 *= .45;

        z *= .42;

        p *= 1.21 + (rz-1.0)*.02;

        rz += tri(p.x+tri(p.y))*z;

        p*= -m2;

    }

    return clamp(1./pow(rz*29., 1.3),0.,.55);

}

float hash21(in vec2 n){ return fract(sin(dot(n, vec2(12.9898, 4.1414))) * 43758.5453); }

vec4 aurora(vec3 ro, vec3 rd)

{

    vec4 col = vec4(0);

    vec4 avgCol = vec4(0);

    for(float i=0.;i<50.;i++)

    {

        float of = 0.006*hash21(gl_FragCoord.xy)*smoothstep(0.,15., i);

        float pt = ((.8+pow(i,1.4)*.002)-ro.y)/(rd.y*2.+0.4);

        pt -= of;

        vec3 bpos = ro + pt*rd;

        vec2 p = bpos.zx;

        float rzt = triNoise2d(p, 0.06);

        vec4 col2 = vec4(0,0,0, rzt);

        col2.rgb = (sin(1.-vec3(2.15,-.5, 1.2)+i*0.043)*0.5+0.5)*rzt;

        avgCol =  mix(avgCol, col2, .5);

        col += avgCol*exp2(-i*0.065 - 2.5)*smoothstep(0.,5., i);

    }

    col *= (clamp(rd.y*15.+.4,0.,1.));

    return col*1.8;

}

vec3 hash33(vec3 p)

{

    p = fract(p * vec3(443.8975,397.2973, 491.1871));

    p += dot(p.zxy, p.yxz+19.27);

    return fract(vec3(p.x * p.y, p.z*p.x, p.y*p.z));

}

vec3 stars(in vec3 p)

{

    vec3 c = vec3(0.);

    float res = iResolution.x*1.;

    for (float i=0.;i<4.;i++)

    {

        vec3 q = fract(p*(.15*res))-0.5;

        vec3 id = floor(p*(.15*res));

        vec2 rn = hash33(id).xy;

        float c2 = 1.-smoothstep(0.,.6,length(q));

        c2 *= step(rn.x,.0005+i*i*0.001);

        c += c2*(mix(vec3(1.0,0.49,0.1),vec3(0.75,0.9,1.),rn.y)*0.1+0.9);

        p *= 1.3;

    }

    return c*c*.8;

}

vec3 bg(in vec3 rd)

{

    float sd = dot(normalize(vec3(-0.5, -0.6, 0.9)), rd)*0.5+0.5;

    sd = pow(sd, 5.);

    vec3 col = mix(vec3(0.05,0.1,0.2), vec3(0.1,0.05,0.2), sd);

    return col*.63;

}

void mainImage( out vec4 fragColor, in vec2 fragCoord )

{

    vec2 q = fragCoord.xy / iResolution.xy;

    vec2 p = q - 0.5;

    p.x*=iResolution.x/iResolution.y;

    vec3 ro = vec3(0,0,-6.7);

    vec3 rd = normalize(vec3(p,1.3));

    rd.xz *= mm2(sin(time*0.05)*0.2);

    vec3 col = vec3(0.);

    vec3 brd = rd;

    float fade = smoothstep(0.,0.01,abs(brd.y))*0.1+0.9;

    col = bg(rd)*fade;

    if (rd.y > 0.){

        vec4 aur = smoothstep(0.,1.5,aurora(ro,rd))*fade;

        col += stars(rd);

        col = col*(1.-aur.a) + aur.rgb;

    }

    else //Reflections

    {

        rd.y = abs(rd.y);

        col = bg(rd)*fade*0.6;

        vec4 aur = smoothstep(0.0,2.5,aurora(ro,rd));

        col += stars(rd)*0.1;

        col = col*(1.-aur.a) + aur.rgb;

        vec3 pos = ro + ((0.5-ro.y)/rd.y)*rd;

        float nz2 = triNoise2d(pos.xz*vec2(.5,.7), 0.);

        col += mix(vec3(0.2,0.25,0.5)*0.08,vec3(0.3,0.3,0.5)*0.7, nz2*0.4);

    }

    fragColor = vec4(col, 1);

}

void main( void ) {

    vec4 colo = vec4(0.0);

    mainImage(colo, gl_FragCoord.xy);

    gl_FragColor = colo;

}