shader_type spatial;

uniform float max_width = .1;
uniform float marker_length = .5;
uniform float pulse_speed = 4.;

void fragment() {
	ALBEDO = vec3(15., 0., 0.);
	vec2 uv = abs(2. * UV.xy - 1.);
	float m_length = marker_length / max_width;
	float anim = sin(TIME * pulse_speed) * .5 + 1.;
	float alpha = step(
		1. - max_width * anim, max(uv.x, uv.y))
			* step(1. - max_width * m_length, min(uv.x, uv.y)
	);
	ALPHA = alpha;
}