// SPECTROGRAM CURTAIN — the audio texture shown almost raw, as the
// waterfall it is: frequency across, time falling down the frame, palette
// mapped straight onto magnitude. The honest picture of the analysis, and
// the one to read when you want to SEE what the other presets are eating.
//
// The only liberties are a slow horizontal fold (so it hangs like cloth)
// and a live edge at the top where the newest row lands.
{
    name: "Spectrogram Curtain"
    engine: "screen"
    seed: 2

    speed: 1.0
    beat_pulse: 0.35
    beat_rate: 1.0
    bar_beats: 4
    glow: 1.0

    p0: 0.5  p1: 0.5  p2: 0.5
    dials: [
        {name: "DEPTH", bind: "p0", default: 0.5},
        {name: "FOLD", bind: "p1", default: 0.5},
        {name: "LIFT", bind: "p2", default: 0.5}
    ]

    color_bg: #x03030a
    color_a: #x1b6bff
    color_b: #xff5a2b
    color_c: #xfff5d0

    stages: [
        {kind: "bloom", threshold: 0.7, strength: 0.8, levels: 2}
    ]

    shader: draw.DrawVjFxScreen {
        fx_color: fn(uv: vec2, content: vec4, cmix: float) -> vec4 {
            // FOLD: a gentle cloth wave, strongest low down.
            let fold = clamp(self.user.y, 0.0, 1.0)
            let sway = sin(uv.y * 7.0 - self.time_beat.x * 0.8) * 0.06 * fold * uv.y
            let x = clamp(uv.x + sway, 0.0, 1.0)

            // DEPTH: how many seconds of history fill the frame.
            let depth = 0.20 + 0.80 * clamp(self.user.x, 0.0, 1.0)
            let age = clamp(uv.y * depth, 0.0, 1.0)
            let v = self.audio_fft(x, age)
            // Idle weave so a silent curtain still has a fabric.
            let idle = 0.045
                + 0.030 * sin(x * 47.0 + age * 30.0)
                + 0.020 * sin(uv.y * 61.0 - self.time_beat.x * 0.7)
            let m = clamp(max(v, idle) * (0.7 + 1.0 * clamp(self.user.z, 0.0, 1.0)), 0.0, 1.0)

            // Three-stop ramp: dark -> cold -> hot -> white.
            let mut rgb = self.col_bg.xyz.mix(self.col_a.xyz, smoothstep(0.0, 0.45, m))
            rgb = rgb.mix(self.col_b.xyz, smoothstep(0.35, 0.80, m))
            rgb = rgb.mix(self.col_c.xyz, smoothstep(0.78, 1.0, m))

            // The live edge: the newest row, drawn hot at the top so you can
            // see the sound ARRIVE.
            let edge = exp(0.0 - uv.y * 90.0)
            let now = self.audio_fft(x, 0.0)
            rgb = rgb + self.col_c.xyz * (edge * (0.15 + 1.1 * now))

            // Vertical seams every octave-ish, so the frequency axis is
            // readable rather than a smear.
            let ticks = smoothstep(0.93, 1.0, abs(sin(x * 12.5664)))
            rgb = rgb + self.col_a.xyz * (ticks * 0.05)
            // The curtain darkens as it falls out of memory.
            rgb = rgb * (1.0 - 0.35 * uv.y * uv.y)
            return vec4(rgb * self.fog.y, 1.0)
        }
    }
}