// SLAT SWEEP L — the frame splits into horizontal slats; every slat
// fills from the right edge leftward at once. COUNT sets the slat count.
{
    name: "Slat Sweep L"
    engine: "transition"
    p1: 0.5
    dials: [
        {name: "SOFT", bind: "p0", default: 0.15},
        {name: "COUNT", bind: "p1", default: 0.5},
        {name: "DIP", bind: "p2", default: 0.0}
    ]
    shader: draw.DrawVjFxDuo {
        trans: fn(uv: vec2, t: float) -> vec4 {
            let n = 5.0 + floor(self.user.y * 15.0)
            let cell = fract(uv.y * n)
            let soft = 0.01 + self.user.x * 0.25
            let field = 1.0 - uv.x
            let tt = t * (1.0 + 2.0 * soft) - soft
            let m = smoothstep(tt - soft, tt + soft, field)
            let seam = smoothstep(0.0, 0.04, cell) * smoothstep(0.0, 0.04, 1.0 - cell)
            let c = self.deck_b(uv).mix(self.deck_a(uv), m)
            let dip = 1.0 - 4.0 * clamp(t, 0.0, 1.0) * (1.0 - clamp(t, 0.0, 1.0)) * self.user.z * 0.9
            let dim = dip * (0.82 + 0.18 * seam)
            return vec4(c.xyz * dim, 1.0)
        }
    }
}