Wave

I like this demo. Very pleasing on the eyes.

To easily create WebGL demos the author created a little library called RGBA.js which is used under the hood.

Focusing on hiding WebGL/JavaScript code from you and giving ability to write fragment shader code only

Once included, this is the only code one has to write:

RGBA(`
float channel(vec2 p, float t) {
  float a = atan(p.x, -p.y);
  float w = sin(a*8.0 + t*2.0)*sin(t+a);  
  float d = length(p) - w*0.013 * smoothstep(0.85, 1.4, abs(a*0.5));
  d = abs(d - 0.25);
  return smoothstep(0.005, 0.0005, d);
}

void main() {
  vec2 p = gl_FragCoord.xy/resolution-0.5;
  p.x *= resolution.x/resolution.y;
  gl_FragColor = vec4(
    channel(p, time*0.7),
    channel(p, time*0.9+1.0),
    channel(p, time*1.1+2.0),
    1.0);
}
`);

More demos in this CodePen Collection