It's impossible to prevent a determined hacker from disassembling a binary. They key things to make it harder are:
* Use full compiler optimisation
* Ensure that there are no debug symbols in the release
* Inline a lot of smaller functions so that there are fewer jumps
* Perhaps encrypt any strings
* Update your release as often as possible
* Compute and store CRC values for files, and force a crash exit if the file does not match a stored CRC - this prevents merely replacing your images and sounds with others.
On the whole, though, it's hardly worth the effort for something with a low sales value
-- Jim DO IT FASTER, EASIER AND BETTER WITH AppGameKit FOR PASCAL