// Compatibility #ifdefs needed for parameters
#ifdef GL_ES
#define COMPAT_PRECISION mediump
#else
#define COMPAT_PRECISION
#endif

// Parameter lines go here:
#pragma parameter RETRO_PIXEL_SIZE "Retro Pixel Size" 0.84 0.0 1.0 0.01
#ifdef PARAMETER_UNIFORM
// All parameter floats need to have COMPAT_PRECISION in front of them
uniform COMPAT_PRECISION float RETRO_PIXEL_SIZE;
#else
#define RETRO_PIXEL_SIZE 0.84
#endif

#if defined(VERTEX)

#if __VERSION__ >= 130
#define COMPAT_VARYING out
#define COMPAT_ATTRIBUTE in
#define COMPAT_TEXTURE texture
#else
#define COMPAT_VARYING varying 
#define COMPAT_ATTRIBUTE attribute 
#define COMPAT_TEXTURE texture2D
#endif

#ifdef GL_ES
#define COMPAT_PRECISION mediump
#else
#define COMPAT_PRECISION
#endif

COMPAT_ATTRIBUTE vec4 VertexCoord;
COMPAT_ATTRIBUTE vec4 COLOR;
COMPAT_ATTRIBUTE vec4 TexCoord;
COMPAT_VARYING vec4 COL0;
COMPAT_VARYING vec4 TEX0;
// out variables go here as COMPAT_VARYING whatever

vec4 _oPosition1; 
uniform mat4 MVPMatrix;
uniform COMPAT_PRECISION int FrameDirection;
uniform COMPAT_PRECISION int FrameCount;
uniform COMPAT_PRECISION vec2 OutputSize;
uniform COMPAT_PRECISION vec2 TextureSize;
uniform COMPAT_PRECISION vec2 InputSize;

// compatibility #defines
#define vTexCoord TEX0.xy
#define SourceSize vec4(TextureSize, 1.0 / TextureSize) //either TextureSize or InputSize
#define OutSize vec4(OutputSize, 1.0 / OutputSize)

void main()
{
    gl_Position = MVPMatrix * VertexCoord;
    TEX0.xy = VertexCoord.xy;
// Paste vertex contents here:
}

#elif defined(FRAGMENT)

#if __VERSION__ >= 130
#define COMPAT_VARYING in
#define COMPAT_TEXTURE texture
out vec4 FragColor;
#else
#define COMPAT_VARYING varying
#define FragColor gl_FragColor
#define COMPAT_TEXTURE texture2D
#endif

#ifdef GL_ES
#ifdef GL_FRAGMENT_PRECISION_HIGH
precision highp float;
#else
precision mediump float;
#endif
#define COMPAT_PRECISION mediump
#else
#define COMPAT_PRECISION
#endif

uniform COMPAT_PRECISION int FrameDirection;
uniform COMPAT_PRECISION int FrameCount;
uniform COMPAT_PRECISION vec2 OutputSize;
uniform COMPAT_PRECISION vec2 TextureSize;
uniform COMPAT_PRECISION vec2 InputSize;
uniform sampler2D Texture;
COMPAT_VARYING vec4 TEX0;
// in variables go here as COMPAT_VARYING whatever

// compatibility #defines
#define Source Texture
#define vTexCoord TEX0.xy

#define SourceSize vec4(TextureSize, 1.0 / TextureSize) //either TextureSize or InputSize
#define OutSize vec4(OutputSize, 1.0 / OutputSize)

// delete all 'params.' or 'registers.' or whatever in the fragment
float iGlobalTime = float(FrameCount)*0.025;
vec2 iResolution = OutputSize.xy;

// Skyline 3D -  FabriceNeyret2 - 2015-07-02
// https://www.shadertoy.com/view/4tlSWr

// in the spirit of the 2D skylines (e.g., https://www.shadertoy.com/view/4tlXzM )... but in 3D :-)  ( I even reproduced the original temporal aliasing :-D  )

// Be sure to wait long enough ;-)

#define T iGlobalTime

// --- using the base ray-marcher of Trisomie21: https://www.shadertoy.com/view/4tfGRB#

vec4 bg = vec4(0); // vec4(0,0,.3,0); 

void mainImage( out vec4 f, vec2 w ) {
    vec4 p = vec4(w,0,1)/iResolution.yyxy-.5, d,c; p.x-=.4; // init ray
    // r(p.xz,.13); r(p.yz,.2); r(p.xy,.1);   // camera rotations
    d =p;                                 // ray dir = ray0-vec3(0)
    p.x += 15.*T; p += 2.*d;
    f = bg;
    float l,x=1e9, closest = 999.;
   
    for (float i=1.; i>0.; i-=.01)  {
       
        vec4 u = floor(p/8.), t = mod(p, 8.)-4., ta; // objects id + local frame
      	u.y = 0.; 
        u = sin(78.17*(u+u.yzxw));                     // randomize ids
        
        c = p/p*1.2;
        ta = abs(t);
        x=1e9; 
        if (sin(17.*(u.x+u.y+u.z))>.95) { // 10% of blocks
            ta.y = p.y + 30.*u.x - .3*pow(abs(.03*floor(p.z)),3.) + 35.;
            x = max(ta.x,max(ta.y,ta.z))  -3.; 
         }
        closest = min(closest, p.y+150.); 
        
        // artifacts: passed a object, we might be fooled about dist to next (hidden in next modulo-tile)
#if 1        // if dist to box border is closest to object, go there.  <<< the working solution ! (at mod8 scale)
        vec4 k, k1 = (4.-t)/d ,k2 = (-4.-t)/d, dd; 
        k = min (k1-1e5*sign(k1),k2-1e5*sign(k2))+1e5; // ugly trick to get the min only if positive.
        // 2 less ugly/costly formulations, but less robust close to /0 :
        //   k = mix(k1,k2, .5+.5*sign(k2));
        //   dd = d+.001*clamp(1.-d*d,.999,1.); k = (4.*sign(dd)-t)/dd;
        l = min(k.x,min(k.y,k.z));
        if (l<x) { p+= 1.*d*(l+0.01); continue; }
#endif
        // if (x<.01) c = texture(iChannel0,.1*(p.xy+p.yz));
      
        if(x<.01) // hit !
            { f = mix(bg,c,i*i); break;  }  // color texture + black fog
       
        p += d*x;       // march ray
     }
    //if (length(f)==0.) f = vec4(1,1,.6,0)*smoothstep(.31,.3,length(w/iResolution.y-vec2(1.3,.7)));
    f += vec4(1) * exp(-.01*closest)*(.5+.5*cos(1.+T/8.)); // thanks kuvkar ! 
}

 void main(void)
{
  //just some shit to wrap shadertoy's stuff
  vec2 FragCoord = vTexCoord.xy*OutputSize.xy;
  mainImage(FragColor,FragCoord);
}
#endif