#version 430 core
layout(location = 0) in vec2 aPos;     // screen pixels, origin top-left
layout(location = 1) in vec2 aUv;
layout(location = 2) in vec4 aColor;

// Campaign V slice V6d: uScreenSize moved into the pinned GpuPushConstants
// block's two spare scalars — uParamA is the framebuffer width in pixels,
// uParamB its height. Vulkan has no default uniform block, so a loose
// `uniform vec2` cannot exist there; the block's fields are the only uniforms
// a shader can read, and the two unclaimed scalars are exactly the right shape.
//
// The arithmetic below is byte-for-byte what it was: the same two divisions and
// the same NDC mapping, reading two floats instead of one vec2.
uniform float uParamA;
uniform float uParamB;

out vec2 vUv;
out vec4 vColor;

void main() {
    // Convert pixel coords (origin top-left, +Y down) to NDC (origin center, +Y up).
    // This is GL-convention NDC on both backends: the Vulkan backend renders with
    // a negative viewport height, so it consumes the same +Y-up clip space and no
    // renderer performs a flip of its own.
    vec2 ndc = vec2(
        aPos.x / uParamA * 2.0 - 1.0,
        1.0 - aPos.y / uParamB * 2.0);
    gl_Position = vec4(ndc, 0.0, 1.0);
    vUv = aUv;
    vColor = aColor;
}