pen(x)

pen(x) = sin(x) * |sin(3x)|

Shader code

shader_type canvas_item;

float Ellipse(vec2 st, bool transparent) {
	vec2 center = vec2(0.5) - st * vec2(1.0, 2.0);
	float value = (0.5 - length(center));
	
	return transparent ? value : (value > 0.0 ? 1.0 : 0.0);
}

float pen(float x) {
	return sin(x) * abs(sin(3.0*x));
}

void fragment()
{
	vec2 st = UV * 2.0;
	//st.y -= 0.5;
	
	float sum = 0.0;
	
	const int ELEMENTS_COUNT = 20;
	const float MARGIN = 0.25;
	
	for(int i=0; i<ELEMENTS_COUNT; i++) {
		float pos = float(i) / float(ELEMENTS_COUNT); // [0.0; 1.0)
		
		float y = ((pos * 2.0) - 1.0) * (1.0 - MARGIN);
		float x = (pen(TIME*5.0 + (float(i) / 30.0)) / 2.0) * (1.0 - pos);
		
		sum += Ellipse(st - vec2(0.5, 0.75) - vec2(x, y), false);
	}
	
	COLOR = vec4(1.0, 0.0, 0.0, sum);
}