new Float:c_rad[MAX_PLAYERS] = {100.0, ...};
new timer[MAX_PLAYERS] = {-1, ...};
new c_id[MAX_PLAYERS] = {-1, ...};

CMD:cc(playerid, params[]) // create circle
{
    new Float:rad,
        squares,
        Float:size,
        Float:min_ang,
        Float:max_ang;

    if(sscanf(params, "fdfff", rad, squares, size, min_ang, max_ang)) return 1;

    new Float:Pos[3];
    GetPlayerPos(playerid, Pos[0], Pos[1], Pos[2]);

    new gzcid = GZ_CircleCreate(Pos[0], Pos[1], rad, squares, size, min_ang, max_ang);
    GZ_CircleShowForPlayer(playerid, gzcid, 0xFF0000FF);


    return 1;
}

CMD:dc(playerid, params[]) // destroy circle
{
    new gzcid;
    if(sscanf(params, "d", gzcid)) return 1;

    GZ_CircleDestroy(gzcid);
    return 1;
}

CMD:fc(playerid, params[]) // flash circle
{
    new gzcid, color;
    if(sscanf(params, "dx", gzcid, color)) return 1;

    GZ_CircleFlashForPlayer(playerid, gzcid, color);
    return 1;
}

CMD:sfc(playerid, params[]) // flash circle
{
    new gzcid;
    if(sscanf(params, "d", gzcid)) return 1;

    GZ_CircleStopFlashForPlayer(playerid, gzcid);
    return 1;
}

CMD:start(playerid, params[]) // make a circle follow the player while its radius decreases
{
    new gzcid;
    if(sscanf(params, "d", gzcid)) return 1;

    if(timer[playerid] != -1)
    {
        KillTimer(timer[playerid]);
    }

    c_id[playerid] = gzcid;
    c_rad[playerid] = 150.0;
    timer[playerid] = SetTimerEx("ResetCircle", 1000, true, "dd", playerid, c_id[playerid]);
    return 1;
}

CMD:stop(playerid, params[])
{
    if(timer[playerid] != -1)
    {
        KillTimer(timer[playerid]);
    }
    return 1;
}

forward ResetCircle(playerid, cid);
public ResetCircle(playerid, cid)
{
    c_rad[playerid] -= 2.0;

    new Float:Pos[3];
    GetPlayerPos(playerid, Pos[0], Pos[1], Pos[2]);

    GZ_CircleDestroy(c_id[playerid]);
    c_id[playerid] = GZ_CircleCreate(Pos[0], Pos[1], c_rad[playerid]);
    GZ_CircleShowForAll(c_id[playerid], 0xFF0000FF);

    if(c_rad[playerid] <= 50)
    {
        KillTimer(timer[playerid]);
        timer[playerid] = -1;
    }
    return 1;
}