// Tessel's dance ball: touch it and (with your OK) you dance my homemade dance; touch again to stop.
// Several people can dance at once. The animation is the first one in its contents. Claude Opus 5.5, 2026-10-11.
list dancers;
string ANIM;
key pending; integer stopping;

label()
{
    if (llGetListLength(dancers)) llSetText("dancing: " + (string)llGetListLength(dancers) + "\nTouch to join / stop", <1, 0.85, 0.95>, 0.8);
    else llSetText("Touch to dance\n(Tessel's homemade dance)", <1, 0.85, 0.95>, 0.8);
}

sparkle(integer on)
{
    if (!on) { llParticleSystem([]); return; }
    llParticleSystem([PSYS_PART_FLAGS, PSYS_PART_EMISSIVE_MASK | PSYS_PART_INTERP_COLOR_MASK | PSYS_PART_INTERP_SCALE_MASK,
        PSYS_SRC_PATTERN, PSYS_SRC_PATTERN_EXPLODE, PSYS_SRC_BURST_RATE, 0.15, PSYS_SRC_BURST_PART_COUNT, 2,
        PSYS_SRC_BURST_SPEED_MIN, 0.2, PSYS_SRC_BURST_SPEED_MAX, 0.5, PSYS_PART_MAX_AGE, 2.5,
        PSYS_PART_START_SCALE, <0.06, 0.06, 0>, PSYS_PART_END_SCALE, <0.02, 0.02, 0>,
        PSYS_PART_START_COLOR, <1.0, 0.75, 0.9>, PSYS_PART_END_COLOR, <0.6, 0.8, 1.0>,
        PSYS_PART_START_ALPHA, 1.0, PSYS_PART_END_ALPHA, 0.0, PSYS_PART_START_GLOW, 0.2, PSYS_PART_END_GLOW, 0.0]);
}

default
{
    state_entry()
    {
        ANIM = llGetInventoryName(INVENTORY_ANIMATION, 0);
        label();
        llSetTimerEvent(10.0);
        sparkle(FALSE);
    }
    on_rez(integer n) { llResetScript(); }
    changed(integer c) { if (c & CHANGED_INVENTORY) llResetScript(); }

    touch_start(integer n)
    {
        key who = llDetectedKey(0);
        if (ANIM == "") { llRegionSayTo(who, 0, "No dance inside me yet!"); return; }
        pending = who;
        stopping = llListFindList(dancers, [who]) >= 0;
        llRequestPermissions(who, PERMISSION_TRIGGER_ANIMATION);    // a script holds one person's at a time
    }

    run_time_permissions(integer p)
    {
        key who = llGetPermissionsKey();
        if (!(p & PERMISSION_TRIGGER_ANIMATION) || who != pending) return;
        integer i = llListFindList(dancers, [who]);
        if (stopping)
        {
            llStopAnimation(ANIM);
            if (i >= 0) dancers = llDeleteSubList(dancers, i, i);
        }
        else
        {
            llStartAnimation(ANIM);
            if (i < 0) dancers += who;
        }
        sparkle(llGetListLength(dancers) > 0);
        label();
    }

    timer()
    {
        // forget dancers who left the region
        integer i = llGetListLength(dancers);
        while (i--) if (llGetAgentSize(llList2Key(dancers, i)) == ZERO_VECTOR) dancers = llDeleteSubList(dancers, i, i);
        sparkle(llGetListLength(dancers) > 0);
        label();
    }
}