/// 建一个用本章 Shader 的粒子系统：Texture Sheet Animation 4×4 + Custom Vertex Streams（UV2 + AnimBlend）
static ParticleSystem MakeSystem(Shot s, Material m, Vector3 pos, float rate, Vector2 life, Vector2 speed, Vector2 size,
                                 Gradient colorOverLife, AnimationCurve sizeOverLife, float coneAngle, float radius, int seed)
{
    var go = new GameObject("Particles");
    go.transform.position = pos;
    go.transform.rotation = Quaternion.Euler(-90, 0, 0);      // Cone 默认沿 +Z 发射，转到朝上
    var ps = go.AddComponent<ParticleSystem>();
    ps.Stop(true, ParticleSystemStopBehavior.StopEmittingAndClear);
    ps.randomSeed = (uint)seed; ps.useAutoRandomSeed = false;

    var main = ps.main;
    main.duration = 5; main.loop = true;
    main.startLifetime = new ParticleSystem.MinMaxCurve(life.x, life.y);
    main.startSpeed = new ParticleSystem.MinMaxCurve(speed.x, speed.y);
    main.startSize = new ParticleSystem.MinMaxCurve(size.x, size.y);
    main.startRotation = new ParticleSystem.MinMaxCurve(0, Mathf.PI * 2);
    main.simulationSpace = ParticleSystemSimulationSpace.World;
    main.maxParticles = 500;

    var em = ps.emission; em.rateOverTime = rate;
    var sh = ps.shape; sh.shapeType = ParticleSystemShapeType.Cone; sh.angle = coneAngle; sh.radius = radius;
    var col = ps.colorOverLifetime; col.enabled = true; col.color = colorOverLife;
    var sz = ps.sizeOverLifetime; sz.enabled = true; sz.size = new ParticleSystem.MinMaxCurve(1, sizeOverLife);

    var tsa = ps.textureSheetAnimation;
    tsa.enabled = true; tsa.numTilesX = 4; tsa.numTilesY = 4;
    tsa.frameOverTime = new ParticleSystem.MinMaxCurve(1, AnimationCurve.Linear(0, 0, 1, 1));

    var r = go.GetComponent<ParticleSystemRenderer>();
    r.sharedMaterial = m;
    r.sortMode = ParticleSystemSortMode.Distance;
    // 与 Shader 里 Attributes 的顺序一一对应
    r.SetActiveVertexStreams(new List<ParticleSystemVertexStream>
    {
        ParticleSystemVertexStream.Position,
        ParticleSystemVertexStream.Color,
        ParticleSystemVertexStream.UV,
        ParticleSystemVertexStream.UV2,
        ParticleSystemVertexStream.AnimBlend,
    });
    return ps;
}