// MURMURATION — STATEFUL GPU particles: 16k particles whose pos/vel/age
// live in a float SIM texture (texel = particle). An update pass
// integrates curl noise + weak centering + a beat kick every frame; the
// draw pass's VERTEX shader fetches each particle's state by instance id
// and stretches the sprite along its velocity. Real momentum — the swarm
// BANKS and REMEMBERS, which no stateless closed form can do. Long `life`
// keeps the flock persistent; feedback paints its history.
{
    name: "Murmuration"
    engine: "simswarm"
    seed: 5

    count: 16384
    size: 0.055
    stretch: 0.05
    speed_color: 0.12

    // The state field's force program (all bindable):
    curl: 1.7
    attract: 0.4
    swirl: 0.12
    gravity: 0.0
    impulse: "(0.6 + pulse * 2.2) * (0.2 + 1.6*p0)"
    drag: 0.5
    max_speed: 7.5
    life: 120.0
    bound: 7.0

    beat_pulse: 0.3
    beat_rate: 0.5

    // PERFORMANCE DIALS — mid-knob = the stock look, exact.
    p0: 0.5  p1: 0.5  p2: 0.5
    dials: [
        {name: "KICK", bind: "p0", default: 0.5},
        {name: "TRAIL", bind: "p1", default: 0.5},
        {name: "GLOW", bind: "p2", default: 0.5}
    ]

    color_bg: #x05070f
    color_a: #x2a4a8f
    color_b: #x6ac8ff
    color_c: #xffffff

    cam_orbit: 0.06
    glow: 1.2

    stages: [
        {kind: "feedback", amount: "min(0.75 + (p1-0.5)*0.44, 0.97)", zoom: 1.004, dim: 0.94},
        {kind: "bloom", threshold: 0.5, strength: "1.25 * (0.25 + 1.5*p2)", levels: 3}
    ]

    // 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 = age 0..1, attr = (id, speed, rnd, state age).
    // 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.DrawVjFxSimSwarmDraw {
        fx_color: fn(t: float, attr: vec4, normal: vec3, wpos: vec3) -> vec4 {
            let sp = clamp(attr.y * self.flow.y, 0.0, 1.0)
            let base = self.col_a.mix(self.col_b, sp)
            let hot = base.xyz + self.col_c.xyz * pow(sp, 3.0) * 0.6
            let fade = smoothstep(0.0, 0.06, t) * (1.0 - smoothstep(0.75, 1.0, t))
            let boost = 0.8 + 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, 0.45, d)
            let halo = 1.0 - smoothstep(0.12, 1.0, d)
            let a = clamp(core + halo * 0.55, 0.0, 1.0) * tint.w
            return vec4(tint.x * a, tint.y * a, tint.z * a, 0.0)
        }
    }
}