Classic Plasma

#define FREQ_X 1.0
#define FREQ_Y 1.0
#define FREQ_DIAG 1.0
#define TIME_SCALE 1.0
const vec3 PALETTE_A = vec3(0.5, 0.5, 0.5);
const vec3 PALETTE_B = vec3(0.5, 0.5, 0.5);
const vec3 PALETTE_C = vec3(1.0, 1.0, 1.0);
const vec3 PALETTE_D = vec3(-0.25, 0.08333, 0.41667);

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
  vec2 uv = (fragCoord - 0.5 * iResolution.xy) / iResolution.y;
  float t = iTime * 0.6 * TIME_SCALE;
  float v = 0.0;
  v += sin((uv.x * FREQ_X + t));
  v += sin((uv.y * FREQ_Y + t) * 0.5);
  v += sin((uv.x + uv.y) * FREQ_DIAG * 0.5 + t * 0.5);
  vec2 c = uv * 5.0 + vec2(sin(t * 0.4), cos(t * 0.5)) * 1.5;
  v += sin(sqrt(c.x * c.x + c.y * c.y + 1.0) + t);
  v *= 0.5;
  vec3 col = PALETTE_A + PALETTE_B * cos(6.28318 * (PALETTE_C * v * 0.5 + PALETTE_D));
  fragColor = vec4(col, 1.0);
}