var_backopacity=0
var_backwatch=0

function fun_backwatch()

if var_backwatch==0
then
var_backopacity=100
wm_transition('FlipFromRight')
var_backwatch=1
else
var_backopacity=0
wm_transition('FlipFromLeft')
var_backwatch=0
end
end 

var_stride = 77
function strideup()
    var_stride = var_stride+1
end
function stridedn()
    if var_stride==0 then
       var_stride=0
    else
       var_stride=var_stride-1
    end
end