#import bevy_pbr::{
    mesh_view_bindings::globals,
    forward_io::VertexOutput,
}

const latitude_cutoff = 50.0;
const tau = 6.283185307179586;

@fragment
fn fragment(in: VertexOutput) -> @location(0) vec4<f32> {
    let color = vec3<f32>(2.0, 6.0, 20.0);
    var alpha = 0.0;

    let lat = 180.0 * abs(in.uv[1] - 0.5);
    let phase = in.uv[0] * 2.0 * 3.14159;
    if (lat > latitude_cutoff) {
        let y = (lat - latitude_cutoff) / (90.0 - latitude_cutoff);
        //alpha = sin(phase * 5.0) + sin(5.0 * y);
        alpha = 0.1 * clamp(-4.0 * cos(tau * sqrt(y + 0.01 * sin(phase * 20.0) + 0.1 * sin(phase))) - 3.0, 0.0, 1.0);
        alpha += 0.3 * clamp(-1000.0 * cos(tau * sqrt(y + 0.01 * sin(phase * 30.0) + 0.1 * sin(phase + 0.3))) - 992.0, 0.0, 1.0);
        alpha += 0.2 * clamp(-1000.0 * cos(tau * sqrt(-0.13 + y + 0.01 * sin(phase * 20.0) + 0.2 * sin(phase + 0.4))) - 992.0, 0.0, 1.0);
    }

    return vec4<f32>(color, clamp(alpha, 0.0, 1.0));
}