precision highp float;

uniform float u_time;
uniform vec2 u_resolution;

float tanh(float x) {
  float exp_neg_2x = exp(-2.0 * x);
  return -1.0 + 2.0 / (1.0 + exp_neg_2x);
}

vec4 tanh_approx(vec4 x) {
  return vec4(tanh(x.x), tanh(x.y), tanh(x.z), tanh(x.w));
}

void main() {
  vec2 fragCoord = gl_FragCoord.xy;
  vec2 iResolution = u_resolution;
  float iTime = u_time;

  vec4 o = vec4(0);

  float z = 5.0;

  float d;

  float i = 0.0;

  vec2 f = (fragCoord - 0.5 * iResolution.xy) / iResolution.y / 0.1;

  vec3 p;

  for (int iter = 0; iter < 100; iter++) {

    p = vec3(f, z);

    p.xz *= mat2(cos(iTime + vec4(0, 33, 11, 0)));

    d = 0.1 + 0.2 * abs((max(abs(p.x) + abs(p.y), abs(p.z)) - 3.5) / 1.732);

    if (d > 0.0) {
      o += (sin(p.y + z + vec4(0, 1, 2, 3)) + 1.0) / d;
    }

    z -= d;
    i += 1.0;

    if (d < 0.01)
      break;
  }

  o = tanh_approx(o * o / 1e5);

  gl_FragColor = o;
}
Prism

Credit
