//modified version of [this shader](https://github.com/wessles/GLSL-CRT/blob/master/shader.frag)
#version 300 es

precision mediump float;
in vec2 v_texcoord;
uniform sampler2D tex;
out vec4 FragColor;

const float scaleFactor = 0.7;

// [0,1]
void main() {
	vec4 cta = texture(tex, v_texcoord);

  // cta += vec4(cos(v_texcoord.x)/4., sin(v_texcoord.y)/4., 0., 1.);
  cta += vec4(cos(v_texcoord.x)/4., cos(v_texcoord.y)/8., sin(v_texcoord.y)/4., 1.);

	FragColor = vec4(clamp(cta.x, 0., 1.), clamp(cta.y, 0., 1.), clamp(cta.z, 0., 1.), clamp(cta.w, 0., 1.));
}