Compared to DELTA, your engine *.exe is
extremely tiny, but I cannot say the same about the images, sounds, and other actual content (maps and layouts take nothing really, they amount to arrays of structures at most, usually only a few KB each).
For comparison, here's what I've got:
DELTA *.exe (current build): 919KB, Release (Optimized -O3), UPX Compressed
All that said, DELTA houses the entire copy of NitroGUI and has several embedded PNG images, so there's much more than just game code in the program. It also has embedded DLL libraries (which accounts for roughly 300KB).
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I'd say that even if you are just under 50MB that would be acceptable given what you are trying to accomplish here, but we also have to think about the users that are not fortunate enough to have a fast internet connection. For some people, they are bandwidth limited. Still others have connections that make 50MB look like you're downloading an entire CD worth of stuff (really slow).
As for the dial-up users with old clunker machines, forget them. They need to get out of the stone age...