shader_type canvas_item;

// Faint red gradient hugging the screen edges, flashed on a hit. `flash` is tweened
// 0.9 → 0 by the HUD; the vignette is transparent in the centre and reddens toward
// the corners so the middle of the screen stays clear.
uniform float flash : hint_range(0.0, 1.0) = 0.0;
uniform vec3 tint : source_color = vec3(0.75, 0.0, 0.0);
uniform float inner : hint_range(0.0, 1.0) = 0.45;
uniform float outer : hint_range(0.0, 1.0) = 1.0;

void fragment() {
	// Distance from centre normalised so the corners land at ~1.0.
	float dist = length(UV - vec2(0.5)) / 0.70710678;
	float v = smoothstep(inner, outer, dist);
	COLOR = vec4(tint, v * flash);
}