//uniform vec2 iMouse;

float sdSphere(vec3 p, float r)
{
    return length(p) - r;
}

float map(vec3 p)
{
    return sdSphere(p, 1.0);
}

vec3 getNormal(vec3 p)
{
    vec2 e = vec2(0.001, 0.0);

    return normalize(vec3(
        map(p + e.xyy) - map(p - e.xyy),
        map(p + e.yxy) - map(p - e.yxy),
        map(p + e.yyx) - map(p - e.yyx)
    ));
}

void mainImage(out vec4 fragColor, in vec2 fragCoord)
{
    vec2 uv = fragCoord.xy / iResolution.xy;
    vec2 p = uv * 2.0 - 1.0;
    p.x *= iResolution.x / iResolution.y;
    
    vec3 ro = vec3(0.0, 0.0, -4.0);
    vec3 rd = normalize(vec3(p, 1.5));
    
    vec2 m = iMouse.xy;
float yaw = (m.x - 0.5) * 1.6;
float pitch = (m.y - 0.5) * 1.0;

rd.xz *= mat2(cos(yaw), -sin(yaw), sin(yaw), cos(yaw));
rd.yz *= mat2(cos(pitch), -sin(pitch), sin(pitch), cos(pitch));

    

    float t = 0.0;
    float hit = 0.0;

    for(int i = 0; i < 80; i++)
    {
        vec3 pos = ro + rd * t;
        float d = map(pos);

        if(d < 0.001)
        {
            hit = 1.0;
            break;
        }

        t += d;

        if(t > 20.0) break;
    }

    vec3 bg = vec3(0.02, 0.03, 0.08);
    vec3 col = bg;

    if(hit > 0.5)
    {
        vec3 pos = ro + rd * t;
        vec3 normal = getNormal(pos);

        vec3 lightDir = normalize(vec3(0.6, 0.8, -0.5));
        float diff = max(dot(normal, lightDir), 0.0);

        float fresnel = pow(1.0 - max(dot(normal, -rd), 0.0), 3.0);

        vec3 base = vec3(0.10, 0.20, 0.85);
        vec3 glow = vec3(0.25, 0.65, 1.0);

        col = base * (0.18 + diff * 0.85);
        col += glow * fresnel * 0.75;
    }

    // Subtle vignette
    float vignette = smoothstep(1.4, 0.2, length(p));
    col *= vignette;

    fragColor = vec4(col, 1.0);
}