[racket] separate big source into several files

hello ~
I am trying to separate big source file into several files
(each files should use each others' definition mutually)

I read racket game source but I could not found way to separating solution
(perhaps since I am a newbie)

If there are
"file-0.rkt", "file-1.rkt", "file-2.rkt", "file-3.rkt", "init.rkt"
in a folder,
I want file-2's button to set file-1's frame as parent,
and want file-3's canvas to set file-1's frame as parent

if I put all of code in a file, it is easy to do it
as like
define f as frame%
define b as button%, f as parent
define c as canvas%, f as parent
if b (button%) is clicked, show something on the c (canvas%)

but this project looks like grow bigger and bigger
so I want to separate this code into many files
for example,
put b (button%) definition and callback function in a separated file,
put c (canvas%) definition in a separated file, etc
and use each others' definition

could somebody give me an little advice?
thanks in advanced
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