out vec4 outcolor;
in vec2 frag_texture_coord;

uniform sampler2D current_frame;
uniform sampler2D previous_frame;
uniform float decay;

void main() {
	vec3 current = texture(current_frame, frag_texture_coord).rgb;
	vec3 previous = texture(previous_frame, frag_texture_coord).rgb;

	// Mix current frame with decayed previous frame
	// Higher decay = more trail (0.5 = subtle, 0.7 = noticeable)
	vec3 result = max(current, previous * decay);

	outcolor = vec4(result, 1.0);
}