integer on;
default
{
    state_entry()
    {
        llSay(0, "Hello, Avatar!");
    }

    touch_start(integer total_number)
    {
        if ( on==0 )
    {
       llSetAlpha(0,ALL_SIDES);
       on=1;
    }
    else
    {
        llSetAlpha(1,ALL_SIDES);
        on=0;
    }
}
}