precision mediump float;

uniform vec2 u_resolution;
uniform float u_time;
uniform vec2 u_mouse;

varying vec2 vUv;

const float PI = 3.1415926;
const float TAU = 6.2831853;

uvec3 k = uvec3(0x456789abu, 0x6789ab45u, 0x89ab4567u);
uvec3 u = uvec3(1, 2, 3);
const uint UINT_MAX = 0xffffffffu;

uint uhash11(uint n){
  n ^= (n << u.x);
  n ^= (n >> u.x);
  n *= k.x;
  n ^= (n << u.x);
  return n * k.x;
}

uvec2 uhash22(uvec2 n){
  n ^= (n.yx << u.xy);
  n ^= (n.yx >> u.xy);
  n *= k.xy;
  n ^= (n.yx << u.xy);
  return n * k.xy;
}

uvec3 uhash33(uvec3 n){
  n ^= (n.yzx << u);
  n ^= (n.yzx >> u);
  n *= k;
  n ^= (n.yzx << u);
  return n * k;
}

float hash11(float p){
  uint n = floatBitsToUint(p);
  return float(uhash11(n)) / float(UINT_MAX);
}

float hash21(vec2 p){
  uvec2 n = floatBitsToUint(p);
  return float(uhash22(n).x) / float(UINT_MAX);
}

float hash31(vec3 p){
  uvec3 n = floatBitsToUint(p);
  return float(uhash33(n).x) / float(UINT_MAX);
}

vec2 hash22(vec2 p){
  uvec2 n = floatBitsToUint(p);
  return vec2(uhash22(n)) / vec2(UINT_MAX);
}

vec3 hash33(vec3 p){
  uvec3 n = floatBitsToUint(p);
  return vec3(uhash33(n)) / vec3(UINT_MAX);
}

float vnoise21(vec2 p){
  vec2 n = floor(p);
  float[4] v;
  for (int j = 0; j < 2; j ++){
    for (int i = 0; i < 2; i++){
      v[i+2*j] = hash21(n + vec2(i, j));
    }
  }
  vec2 f = fract(p);
  f = f * f * f * (10.0 - 15.0 * f + 6.0 * f * f);
  return mix(mix(v[0], v[1], f[0]), mix(v[2], v[3], f[0]), f[1]);
}
//end vnoise

//start processing noise
float base21(vec2 p){
  return vnoise21(p) - 0.5;
}

float fbm21(vec2 p, float g){
  float val = 0.0;
  float amp = 1.0;
  float freq = 1.0;
  for (int i = 0; i < 4; i++){
    val += amp * base21(freq * p);
    amp *= g;
    freq *= 2.01;
  }
  return 0.5 * val + 0.5;
}

float warp21(vec2 p, float g){
  float val = 0.0;
  for (int i = 0; i < 3; i++){
    val = fbm21(p + g * vec2(cos(TAU * val), sin(TAU * val)), 0.5);
  }
  return val;
}
//end processing noise

//start cnoise
float fdist31(vec3 p){
  vec3 n = floor(p + 0.5);
  float dist = sqrt(3.0);
  for(float k = 0.0; k <= 2.0; k ++ ){
    vec3 glid;
    glid.z = n.z + sign(mod(k, 2.0) - 0.5) * ceil(k * 0.5);
    if (abs(glid.z - p.z) - 0.5 > dist){
      continue;
    }
    for(float j = 0.0; j <= 2.0; j ++ ){
      glid.y = n.y + sign(mod(j, 2.0) - 0.5) * ceil(j * 0.5);
      if (abs(glid.y - p.y) - 0.5 > dist){
        continue;
      }
      for(float i = -1.0; i <= 1.0; i ++ ){
        glid.x = n.x + i;
        vec3 jitter = hash33(glid) - 0.5;
        dist = min(dist, length(glid + jitter - p));
      }
    }
  }
  return dist;
}

vec2 rot2(vec2 p, float t) {
  return vec2(cos(t) * p.x - sin(t) * p.y, sin(t) * p.x + cos(t) * p.y);
}

vec3 rotX(vec3 p, float t) {
  return vec3(p.x, rot2(p.yz, t));
}

float text(vec2 st) {
  float time = 0.3 * u_time;
  return fdist31(vec3(st + time, time));
}

void main() {
  vec2 pos = (2.0 * gl_FragCoord.xy - u_resolution.xy) / min(u_resolution.x, u_resolution.y);

  vec3 cPos = vec3(0.0, 0.0, 0.0);
  float t = -0.25 * PI;
  vec3 cDir = rotX(vec3(0.0, 0.0, -1.0), t);
  vec3 cUp = rotX(vec3(0.0, 1.0, 0.0), t);
  vec3 cSide = cross(cDir, cUp);
  float targetDepth = 1.0;
  vec3 ray = cSide * pos.x + cUp * pos.y + cDir * targetDepth - cPos;
  ray = normalize(ray);

  vec3 groundNormal = vec3(0.0, 1.0, 0.0);
  float groundHeight = 1.5;
  vec3 lPos = vec3(0.0);
  vec3 col;

  if (dot(ray, groundNormal) < 0.0) {
    vec3 hit = cPos - ray * groundHeight / dot(ray, groundNormal);
    float diff = max(dot(normalize(lPos - hit), groundNormal), 0.0);
    diff *= 1.2;
    diff = pow(diff, 0.8);
    col = vec3(diff * text(hit.zx));
  } else {
    col = vec3(0.0);
  }

  gl_FragColor = vec4(col, 1.0);
}