struct Particle {
    pos: vec3<f32>,
    _pad0: f32,       // matches _pad0 in C
    vel: vec3<f32>,
    _pad1: f32,       // matches _pad1 in C
};

@group(0) @binding(0)
var<storage, read> particles: array<Particle>;

@group(0) @binding(1)
var<uniform> viewProjectionMatrix: mat4x4<f32>;

@group(0) @binding(2)
var<uniform> cameraRight: vec3<f32>;

@group(0) @binding(3)
var<uniform> cameraUp: vec3<f32>;

struct VertexOutput {
    @builtin(position) Position: vec4<f32>,
    @location(0) fragColor: vec4<f32>,
};

const quadVertexOffsets = array<vec2<f32>, 6>(
    vec2<f32>(-1, -1),
    vec2<f32>( 1, -1),
    vec2<f32>(-1,  1),
    vec2<f32>( 1, -1),
    vec2<f32>( 1,  1),
    vec2<f32>(-1,  1)
);

@vertex
fn vs_main(
    @builtin(vertex_index) vertexIndex: u32,
    @builtin(instance_index) instanceIndex: u32
) -> VertexOutput {
    let particle = particles[instanceIndex];


    let offset = quadVertexOffsets[vertexIndex];

let worldPosition = particle.pos * 150.0
    + offset.x * cameraRight
    + offset.y * cameraUp;

    var output: VertexOutput;
    output.Position = viewProjectionMatrix * vec4<f32>(worldPosition , 1.0);
    output.fragColor = vec4<f32>(1.0, 1.0, 1.0, 1.0); // white color

    return output;
}

@fragment
fn fs_main(input: VertexOutput) -> @location(0) vec4<f32> {
    return input.fragColor;
}
