// WORMHOLE — a (3,2) torus-knot tube flown from the inside; neon rings
// sweep toward you ON THE BEAT (the ring phase rides beat position, not
// wall time, so a tempo change changes the flight).
{
    name: "Wormhole"
    engine: "tunnel"

    knot_p: 3.0
    knot_q: 2.0
    major: 7.0
    tube: 1.5
    rings: 900
    sides: 24
    fly: 4.0
    bands: 110.0

    beat_pulse: "0.7 * (0.2 + 1.6*p0)"
    beat_rate: 1.0
    // PERFORMANCE DIALS — mid-knob = the stock look, exact.
    p0: 0.5  p1: 0.5  p2: 0.5
    dials: [
        {name: "PUMP", bind: "p0", default: 0.5},
        {name: "GLOW", bind: "p1", default: 0.5},
        {name: "TRAIL", bind: "p2", default: 0.5}
    ]

    color_bg: #x030014
    color_a: #x8040ff
    color_b: #x30f0ff
    color_c: #xff40a0

    fog: 0.10
    glow: "1.3 * (0.25 + 1.5*p1)"

    stages: [
        {kind: "bloom", threshold: 0.4, strength: 1.6, levels: 3},
        {kind: "feedback", amount: "min(0.45 + (p2-0.5)*0.8, 0.97)", zoom: 1.015, rotate: 0.0, 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 = along the bore 0..1, attr = (around, along, ring hash,
    // radius), content = the wall texel at this vertex, cmix = the
    // pre-gated content strength (0 without real channel video). The
    // wall DRAPE has its own pixel hook, `fx_wall` — this tunnel keeps
    // the stock one.
    // 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.DrawVjFxTunnel {
        fx_color: fn(t: float, attr: vec4, normal: vec3, wpos: vec3,
                     content: vec4, cmix: float) -> vec4 {
            return self.col_a.mix(self.col_b, t)
        }
    }
}