// FIREWORKS — staggered burst shells, stateless GPU particles.
// The vertex shader re-derives every spark from (id, seed, time); the CPU
// uploaded one quad per particle once and will never touch it again.
{
    name: "Fireworks"
    engine: "particles"
    mode: "burst"
    seed: 12

    count: 9000
    spread: 7.0
    size: 0.14
    rate: 0.35
    gravity: 1.1

    speed: 1.0
    // PERFORMANCE DIALS — p0..p2 route through binding expressions; each
    // default reproduces the stock look exactly (dials only act when moved).
    beat_pulse: "0.65 * (0.2 + 1.6*p0)"
    beat_rate: 1.0
    p0: 0.5  p1: 0.5  p2: 0.5
    dials: [
        {name: "PUMP", bind: "p0", default: 0.5},
        {name: "TRAIL", bind: "p1", default: 0.5},
        {name: "GLOW", bind: "p2", default: 0.5}
    ]

    color_bg: #x040308
    color_a: #xffd24a
    color_b: #x66aaff
    color_c: #xfff6e0

    cam_dist: 16.0
    cam_height: 3.5
    cam_orbit: 0.05
    fog: 0.02

    stages: [
        {kind: "bloom", threshold: 0.35, strength: "1.6 * (0.25 + 1.5*p2)", levels: 3},
        {kind: "feedback", amount: "min(0.55 + (p1-0.5)*0.7, 0.97)", zoom: 1.0, rotate: 0.0, dim: 0.9}
    ]

    // THE LOOK LIVES HERE. This block is not a reference to the
    // engine's shader — it IS the pixel math this effect runs.
    // Rewrite it and the effect looks different; everything else
    // (geometry, motion, the content coupling, the beat) keeps
    // working, because the block SUBCLASSES the engine shader.
    // Inputs: t = life 0..1, attr = (id, spawn phase, hue, rnd).
    // Signals: self.time_beat (time, beat, phase, pulse),
    // self.sig (bar, bpm, energy, dt), self.user (p0..p3),
    // self.col_a/b/c/bg, self.fog (density, glow, content, -).
    shader: draw.DrawVjFxParticles {
        fx_color: fn(t: float, attr: vec4, normal: vec3, wpos: vec3) -> vec4 {
            let base = self.col_a.mix(self.col_b, attr.z)
            let hot = base.xyz + vec3(0.5, 0.4, 0.3) * pow(1.0 - t, 6.0)
            let fade = (1.0 - t) * smoothstep(0.0, 0.08, t)
            let boost = 0.85 + self.time_beat.w * 0.9
            return vec4(hot * boost, fade)
        }

        fx_sprite: fn(uv: vec2, tint: vec4) -> vec4 {
            let d = length(uv - vec2(0.5, 0.5)) * 2.0
            let core = 1.0 - smoothstep(0.0, 0.5, d)
            let halo = 1.0 - smoothstep(0.15, 1.0, d)
            let a = clamp(core + halo * 0.5, 0.0, 1.0) * tint.w
            return vec4(tint.x * a, tint.y * a, tint.z * a, 0.0)
        }
    }
}