program define coins
    version 4.0

    quietly{
        set obs 100
        gen x=uniform()
        gen y=uniform()}

    global n=1
    global ntot=0
    global xtot=0
        
    wdctl button "Reset"  5  5 30 12 HJN_B0
    wdctl button "Flip" 5 20 30 12 HJN_B1
    wdctl button "Help"   5 35 30 12 HJN_B5
    wdctl button "Close"  5 50 30 12 HJN_B6
    global n=1
    global HJN_1 "# of flips"
    wdctl static HJN_1 5 65 30 12 
    wdctl edit n      40 65 10 12
        
    global HJN_B0 "coinsdr 0"
    global HJN_B1 "coinsdr 1"
    global HJN_B5 "whelp coins"
    global HJN_B6 "exit 1234"

    noi wdlg "Flipping Coins"  5 5 80 130

    restore

end

program define coinsdr
    version 4.0

    local arg = `1'

    if `arg'==0 {
        global ntot=0
        global xtot=0}

    if $n < 1  $n > 500 {
        sstopbox stop "# of flips must be between 1 and 500"
        exit}    
        
    replace x=.
    replace y=.
    replace x=uniform() in 1/10
    replace y=uniform() in 1/10
    gph open
    gph pen
    graph y x, s(i) xlab(0,1) ylab(0,.5,1)

    replace x=.
    replace y=.
    replace x=uniform() in 1/$n
    replace y=uniform() in 1/$n