// BAR CURTAIN V — horizontal bars close toward alternating edges: even
// bars slide in from the top, odd bars from the bottom. SAW staggers
// each bar's start by a per-bar hash so the curtain does not close in
// lockstep.
{
    name: "Bar Curtain V"
    engine: "transition"
    p1: 0.5
    dials: [
        {name: "SOFT", bind: "p0", default: 0.15},
        {name: "BARS", bind: "p1", default: 0.5},
        {name: "SAW", bind: "p2", default: 0.3}
    ]
    shader: draw.DrawVjFxDuo {
        trans: fn(uv: vec2, t: float) -> vec4 {
            let n = 6.0 + floor(self.user.y * 14.0)
            let row = floor(uv.y * n)
            let celly = fract(uv.y * n)
            let parity = modf(row, 2.0)
            let local = mix(celly, 1.0 - celly, parity)
            let soft = 0.02 + self.user.x * 0.3
            let hash = fract(sin(row * 12.9898 + 4.0) * 43758.5453)
            let saw = (hash - 0.5) * self.user.z * 0.6
            let tt = t * (1.0 + 2.0 * soft) - soft + saw
            let m = smoothstep(tt - soft, tt + soft, local)
            let c = self.deck_b(uv).mix(self.deck_a(uv), m)
            return vec4(c.xyz, 1.0)
        }
    }
}