animated_circle.frag

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;
uniform float u_time;

float draw_circle(vec2 position, float radius) {
	return step(radius, length(position - vec2(.5)));
}

void main() {
	vec2 position = gl_FragCoord.xy / u_resolution;

	float r = abs(.5 + cos(u_time * .9));
	r *= .4;

	position.x += .2 * cos(u_time * .8) * .2;
	position.y += .4 * sin(u_time * .4 * sin(u_time * .01)) * .4;

	float circle = draw_circle(position, .02 + r);

	gl_FragColor = vec4(vec3(circle), 1.);
}