#version 460 core

#include "consts.h"

layout(location = 0) out vec4 color;
in vec4 gl_FragCoord;

layout(location = U_LOC_TIME) uniform float time;
layout(location = U_LOC_PASS1) uniform sampler2D buf;
ivec2 res = ivec2(RES_H, RES_V);

const float step = 0.04;
const float turns = 9.0;

void main() {
	vec2 uv = gl_FragCoord.xy / res.xy;
	float r = 20.0; // circle radius
	
	vec2 norm = (uv - 0.5) * 2.0;
	norm.x *= float(res.x) / float(res.y); // adjust for aspect ratio

	float offset = time * 7.0;

	float mag = 1.3 + 0.5 * sin(2 * time);
	float size = 0.4 + 0.1 * sin(3 * time);

	color = vec4(0.0);

	for (float t = 0.0; t < PI_2; t += step) {
		// <https://www.desmos.com/calculator/e0kq6z1ndd>
		vec2 f = vec2(
			cos(t) + mag * cos(turns * t + offset),
			sin(t) + mag * sin(turns * t + offset)
		);
		f *= size;
		if (length(f - norm) < 0.01) {
			color = vec4(1.0, 1.0, 1.0, 1.0);
		}
	}

	color += texture(buf, ((uv - 0.5) * 0.99) + 0.5) * 0.97;
}