// INK DROP — the STABLE-FLUIDS engine: advect, divergence, a budgeted
// jacobi pressure solve (`iters`) and projection run on a float GPU grid
// every frame; dye splats inject ON THE KICK at a per-beat hashed point,
// in a palette color that cycles per beat. The ink then genuinely FLOWS —
// filaments curl, collide and fade like drops in dark water.
{
    name: "Ink Drop"
    engine: "fluid"
    seed: 4

    grid: 176
    iters: 24

    force: 2.6
    dissipation: 0.10
    swirl: 0.35
    splat: "(2.2 + pulse * 0.9) * (0.2 + 1.6*p2)"
    dye_fade: 0.12
    radius: 0.075
    vortex: 3.2

    beat_pulse: 0.4
    beat_rate: 0.5

    // p0 = flow-warp of the (unused) input, p1 = input mix: pure ink here.
    p0: 0.0
    p1: 0.0
    p2: 0.5

    // PERFORMANCE DIALS — WARP/MIX are the fluid engine's own p0/p1
    // levers (MIX up brings the channel content through the ink, WARP
    // bends it with the flow); SPLAT routes p2 through the dye splats.
    dials: [
        {name: "WARP", bind: "p0", default: 0.0},
        {name: "MIX", bind: "p1", default: 0.0},
        {name: "SPLAT", bind: "p2", default: 0.5}
    ]

    color_bg: #x06060a
    color_a: #x30c8ff
    color_b: #xff3a9a
    color_c: #xb0ff5a

    glow: 2.6

    stages: [
        {kind: "bloom", threshold: 0.6, strength: 1.0, levels: 2}
    ]

    // 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: uv, the dye and flow texels, and the base under the ink.
    // 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.DrawVjFxFluidView {
        fx_shade: fn(uv: vec2, dye: vec4, flow: vec4, base: vec3) -> vec4 {
            let glow = self.u_view.x
            let ink = vec3(dye.x, dye.y, dye.z) * glow
            let shimmer = clamp(length(flow.xy) * 0.35, 0.0, 0.6)
            let mut lit = ink + ink * shimmer
            // Soft-knee tone map: color survives density; only genuinely
            // dense ink approaches white.
            lit = lit / (vec3(1.0, 1.0, 1.0) + lit * 0.45)
            let rgb = vec3(1.0, 1.0, 1.0)
                - (vec3(1.0, 1.0, 1.0) - base)
                * clamp(vec3(1.0, 1.0, 1.0) - lit, vec3(0.0, 0.0, 0.0), vec3(1.0, 1.0, 1.0))
            return vec4(rgb, 1.0)
        }
    }
}