var g_arr0=[1,2,3,4,5];
var g_arr1=[]; // the left stack
var g_arr2=[]; // the right stack
var g_z=1; // used to set z-index
// used to position the falling discs correctly
//   see drop(id)
var g_margin=0;
// keeps track of the falling discs
//   see next1()
var g_ind=0;
var g_ans; // 'left' or 'right'
// the falling array - see play()
var g_arr;
// the body element
//   used to change the background colour
var g_body_el;