Try at http://glslsandbox.com

#ifdef GL_ES
precision highp float;
#endif

uniform float time;
uniform vec2 resolution;

void main( void ) {

	vec2 p = (gl_FragCoord.xy*2.0-resolution)/resolution.y;
	float r = length(p);
	float a = atan(p.y,p.x);
	float s = sin(time*.2)*4.+sin(12.*a);
	float c = abs(sin(r*s));
	gl_FragColor = vec4(c);
}