shader_type spatial;
render_mode unshaded, cull_disabled;

// Correct Godot 4.2+ screen texture
uniform sampler2D screen_tex : hint_screen_texture;

// Controls
uniform float distortion_strength : hint_range(0.0, 6.0) = 0.75;
uniform float swirl_strength : hint_range(0.0, 10.0) = 2.0;
uniform float noise_amount : hint_range(0.0, 3.0) = 0.3;
uniform float fog_density : hint_range(0.0, 6.0) = 1.0;

uniform vec4 tint_color : source_color = vec4(1.0);

// Procedural noise
float hash(vec2 p) {
    p = fract(p * vec2(123.34, 345.45));
    p += dot(p, p + 34.345);
    return fract(p.x * p.y);
}

void fragment() {
    vec2 uv = UV;
    vec2 centered = uv - vec2(0.5);
    float r = length(centered);

    // --- Fresnel (stronger distortion at edges) ---
    float fresnel = pow(1.0 - abs(dot(NORMAL, VIEW)), 2.0);

    // --- Swirl continuation ---
    float angle = atan(centered.y, centered.x);
    angle += swirl_strength * TIME;
    vec2 swirl_dir = vec2(cos(angle), sin(angle));

    // --- Procedural noise ---
    float n = hash(uv * 10.0 + TIME * 0.2);

    // --- Final distortion vector ---
    vec2 distortion =
        centered * distortion_strength * fresnel +
        swirl_dir * 0.1 * distortion_strength +
        (n - 0.5) * noise_amount;

    // --- Sample the world behind the sphere ---
    vec3 scene_col = texture(screen_tex, SCREEN_UV + distortion).rgb;

    // --- Fog fade (applied LAST so it doesn't darken the distortion) ---
    float fog = smoothstep(0.0, fog_density, r);
    scene_col = mix(scene_col, tint_color.rgb, fog * 0.5);

    // --- Soft alpha fade ---
    float alpha = smoothstep(1.0, 0.3, r);

    ALBEDO = scene_col;
    ALPHA = alpha * tint_color.a;
}