struct Uniforms {
  resolution: vec2<f32>,
  time: f32,
  scene: f32,
  mouse: vec2<f32>,
  date: vec4<f32>,
  sampleRate: vec4<f32>,
  stemMultipliers: array<vec4<f32>, 8>,
};

@group(0) @binding(0) var<uniform> u: Uniforms;

struct VsOut {
  @builtin(position) pos: vec4<f32>,
  @location(0) uv: vec2<f32>,
};

@vertex
fn vs(@builtin(vertex_index) i: u32) -> VsOut {
  let p = array<vec2<f32>, 3>(
    vec2<f32>(-1.0, -3.0),
    vec2<f32>(-1.0, 1.0),
    vec2<f32>(3.0, 1.0),
  );
  let clip = p[i];
  var out: VsOut;
  out.pos = vec4<f32>(clip, 0.0, 1.0);
  out.uv = clip;
  return out;
}

@fragment
fn fs(in: VsOut) -> @location(0) vec4<f32> {
  let res = u.resolution;
  let fragCoord = (in.uv * vec2<f32>(0.5) + vec2<f32>(0.5)) * res;

  var uv = (fragCoord - 0.5 * res) / res.y;

  let slowTime = u.time * 0.2;

  let bgGrey = vec3<f32>(0.11, 0.11, 0.12);
  let cardGrey = vec3<f32>(0.30, 0.32, 0.36);
  let coreWhite = vec3<f32>(0.90, 0.95, 0.90);

  // ---------- palette keyed by scene ----------
  let scene0 = vec3<f32>(0.20, 0.75, 0.20);   // HERO   – emerald
  let scene1 = vec3<f32>(0.85, 0.55, 0.20);   // ABOUT  – amber
  let scene2 = vec3<f32>(0.25, 0.60, 0.95);   // PROJECTS – cobalt
  let scene3 = vec3<f32>(0.90, 0.35, 0.55);   // CONTACT – rose

  let sFloor = i32(clamp(floor(u.scene), 0.0, 3.0));
  let sCeil  = i32(clamp(ceil(u.scene), 0.0, 3.0));
  var c0 = scene0;
  c0 = select(c0, scene1, sFloor == 1);
  c0 = select(c0, scene2, sFloor == 2);
  c0 = select(c0, scene3, sFloor == 3);
  var c1 = scene0;
  c1 = select(c1, scene1, sCeil == 1);
  c1 = select(c1, scene2, sCeil == 2);
  c1 = select(c1, scene3, sCeil == 3);
  let tBlend = u.scene - floor(u.scene);
  let sceneAccent = mix(c0, c1, tBlend * tBlend * (3.0 - 2.0 * tBlend));

  // ---------- mouse-reactive distortion ----------
  let mousePos = (u.mouse - 0.5 * res) / res.y;
  let distMouse = length(uv - mousePos);
  let influence = exp(-distMouse * 7.0);
  uv += (mousePos - uv) * influence * 0.12;

  let angle = atan2(uv.y, uv.x);
  let radius = length(uv);

  let baseSpiral = angle + (radius * 8.0) - slowTime;
  let ripple = sin(radius * 15.0 - (u.time * 0.5)) * 0.08;
  let distortedSpiral = baseSpiral + ripple;

  let armCount = 2.0;
  let rChannel = smoothstep(0.05, 0.55, abs(sin((distortedSpiral + 0.04) * armCount)));
  let gChannel = smoothstep(0.05, 0.55, abs(sin(distortedSpiral * armCount)));
  let bChannel = smoothstep(0.05, 0.55, abs(sin((distortedSpiral - 0.04) * armCount)));
  let patternChannels = vec3<f32>(rChannel, gChannel, bChannel);

  let coreNeon = vec3<f32>(0.02 / (patternChannels + 0.025));
  let spiralColor = mix(cardGrey, sceneAccent, patternChannels.g);
  let primarySpiral = coreNeon * spiralColor;

  let ringWave = sin(radius * 12.0 - (u.time * 1.5));
  let sharpRing = smoothstep(0.85, 0.95, ringWave);
  let ringMask = sharpRing * smoothstep(0.7, 0.1, radius);
  let secondaryRings = cardGrey * ringMask * 0.4;

  let vignette = smoothstep(0.95, 0.4, radius);

  var finalColor = bgGrey + secondaryRings;
  finalColor = mix(finalColor, primarySpiral, 0.85);

  let centerLight = 0.015 / (radius + 0.02);
  finalColor += centerLight * coreWhite;

  // soft cursor glow
  finalColor += exp(-distMouse * 4.0) * 0.03 * sceneAccent;

  // ---------- dim when not on the home page (u.date.x controls it) ----------
  let dim = u.date.x;
  finalColor = mix(finalColor, vec3<f32>(0.0), dim);

  return vec4<f32>(finalColor * vignette, 1.0);
}