red in black

precision highp float;
uniform vec2  u_resolution;
uniform float u_time;
uniform vec3  u_colors[4];

vec3 shade(vec2 uv, vec2 p, float t) {
  // ····· ··· ···· ·· ······· ····· ·· ·····
  float v = fbm(p * ····· + t * ····);
  return palette(0.5 + 0.5 * sin(v + ·····));
}