#version 330

uniform sampler2D texture0;
uniform vec2 resolution;
uniform float time;

// Screen-space UV of the sun — kept off in a corner like a low sun rather
// than dead center, so the rays read as directional light rather than a
// starburst sitting on top of the view. This shader samples the already-
// rendered scene texture (RenderPostFX draws it via a source rect with a
// negative height to correct raylib's render-texture V-flip for texture0
// itself), but fragTexCoord's V still runs top-of-screen=0 in that same
// flipped sense — so a Y near 0 here actually lands near the BOTTOM of
// what's on screen; 0.88 is what puts the sun near the top.
uniform vec2 sunScreenPos = vec2(0.82, 0.88);
uniform float rayCount = 10.0;
uniform float raySharpness = 3.0;
uniform float rayStrength = 0.35;
uniform float raySpeed = 0.03;

in vec2 fragTexCoord;
out vec4 finalColor;

void main()
{
    vec2 uv = fragTexCoord;
    vec4 baseColor = texture(texture0, uv);

    // Cheap screen-space light shafts: no scene depth/occlusion to sample,
    // so this fakes them as angular streaks radiating from the sun position
    // that fade out with distance, rather than true raymarched shafts.
    vec2 aspectFix = vec2(resolution.x / resolution.y, 1.0);
    vec2 toSun = (uv - sunScreenPos) * aspectFix;
    float dist = length(toSun);
    float angle = atan(toSun.y, toSun.x);

    float streaks = sin(angle * rayCount + time * raySpeed) * 0.5 + 0.5;
    streaks = pow(streaks, raySharpness);

    float falloff = clamp(1.0 - dist * 0.9, 0.0, 1.0);
    falloff *= falloff;

    vec3 rayColor = vec3(1.0, 0.92, 0.75) * streaks * falloff * rayStrength;
    finalColor = vec4(baseColor.rgb + rayColor, baseColor.a);
}