shader_type canvas_item;
render_mode unshaded;

uniform sampler2D screen_texture : hint_screen_texture, filter_linear;
uniform float chromatic_aberration : hint_range(0.0, 0.02) = 0.0;
uniform float vignette_strength : hint_range(0.0, 1.0) = 0.22;


void fragment() {
	vec2 radial = UV - vec2(0.5);
	vec2 chroma = radial * chromatic_aberration;
	vec4 center = texture(screen_texture, UV);
	vec3 color = center.rgb;
	// The branch is driven by one uniform for the whole draw, so non-turbo
	// frames avoid two redundant screen taps without causing warp divergence.
	if (chromatic_aberration > 0.0001) {
		color.r = texture(screen_texture, UV + chroma).r;
		color.b = texture(screen_texture, UV - chroma).b;
	}

	// Aspect-correct vignette, always subtle and tightened slightly on turbo.
	vec2 aspect_radial = radial;
	aspect_radial.x *= SCREEN_PIXEL_SIZE.y / SCREEN_PIXEL_SIZE.x;
	float vignette = smoothstep(0.38, 0.78, length(aspect_radial));
	color *= 1.0 - vignette * vignette_strength;
	COLOR = vec4(color, 1.0);
}