// Simple UV gradient shader (vertex + fragment)

struct VertexInput {
    @location(0) position: vec3<f32>,
    @location(1) uv: vec2<f32>,
}

struct VertexOutput {
    @builtin(position) clip_position: vec4<f32>,
    @location(0) uv: vec2<f32>,
}

@vertex
fn vertex(in: VertexInput) -> VertexOutput {
    var out: VertexOutput;
    // assume incoming positions are in clip-space (vec3 with z, or model-transformed)
    out.clip_position = vec4<f32>(in.position, 1.0);
    out.uv = in.uv;
    return out;
}

@fragment
fn fragment(in: VertexOutput) -> @location(0) vec4<f32> {
    // very simple vertical gradient between two colors
    let bottom = vec3<f32>(1.0, 0.8, 0.2); // warm
    let top    = vec3<f32>(0.2, 0.6, 1.0); // cool

    let color = mix(bottom, top, in.uv.y);
    return vec4<f32>(color, 1.0);
}