// DRAGON COIL — the dragon-curve rewriting system drawn as a glowing
// space-filling ribbon. Pattern taught: structure symbols X/Y carry the
// program; only F draws — 90-degree angles give the classic fold.
{
    name: "Dragon Coil"
    engine: "lsystem"
    seed: 3

    axiom: "FX"
    rules: ["X=X+YF+", "Y=-FX-Y"]
    iterations: 12
    angle: 90.0
    step: 0.10
    radius: 0.035
    sides: 4

    grow: "loop"
    grow_beats: 16
    sway: 0.15
    sway_freq: 0.4
    beat_pulse: "0.5 * (0.2 + 1.6*p1)"
    twist: 0.04
    // PERFORMANCE DIALS — mid-knob = the stock look, exact.
    p0: 0.5  p1: 0.5  p2: 0.5
    dials: [
        {name: "TRAIL", bind: "p0", default: 0.5},
        {name: "PUMP", bind: "p1", default: 0.5},
        {name: "GLOW", bind: "p2", default: 0.5}
    ]

    color_bg: #x0a0312
    color_a: #xff3fd8
    color_b: #x3fd8ff
    color_c: #xffffff

    cam_orbit: 0.11
    fog: 0.03
    glow: "1.35 * (0.25 + 1.5*p2)"

    stages: [
        {kind: "bloom", threshold: 0.45, strength: 1.4, levels: 3},
        {kind: "feedback", amount: "min(0.45 + (p0-0.5)*0.8, 0.97)", zoom: 1.003, rotate: 0.002, dim: 0.94}
    ]

    // 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 = arc from the root 0..1, attr = (depth, arc, hue, tube radius).
    // 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.DrawVjFxMesh {
        fx_displace: fn(pos: vec3, normal: vec3, attr: vec4) -> vec3 {
            return vec3(0.0, 0.0, 0.0)
        }

        fx_color: fn(t: float, attr: vec4, normal: vec3, wpos: vec3) -> vec4 {
            let base = self.col_a.mix(self.col_b, clamp(attr.z, 0.0, 1.0))
            let tip = self.col_c * (clamp(t, 0.0, 1.0) * 0.35)
            let flash = self.col_c * (self.time_beat.w * 0.5)
            return vec4(base.xyz + tip.xyz + flash.xyz, 1.0)
        }
    }
}