> When you say can't handle it you mean: won't
> download, or will download but mistakes can happen
> and can't be solved?> (just to make sure if it's hopeless)

Flash is, or at least used to be, a proprietary, closed, binary format.
Httrack can download a swf file, but it doesn't know how to interpret it and
thus can't know what resources it on turn requires.

Morever:
1. swf files (especially when used for a game) are usually applications, and
when it is so it's in general impossible to predict what online resources they
will need
2. they frequently need things generated dinamically by a server, based on
some state, time or whatnot; these cannot be meaningfully downloaded, you can
download an instance but it won't work at later times.

These last two points actually apply equally to javascript, and indeed you'll
very often not be able to download and use offline a complex web application,
game or simply dynamic page.

As to the first point, I actually found out that at least a part of the
formats has been publicly documented, and parts have been figured out
independently by some developers, and there are thus several open-source
applications that can interpret or disassemble at least some of them (I don't
know if this is completely new to me or I had just forgotten about it).
So, it's a problem that could theoretically be in part fixable, but it will
almost for sure never happen for httrack because:
- it is by all indications a dead software
- and if it were ever to up developed further there are far more pressing, and
simpler, issues.

Your best recourse is to contact the authors of the game and ask them to
release its source code; you'll then at least have a way to put it back online
if the current site were ever to be shut down.


By way I tried to have a look at that specific site, to see if there was
something easy that could be done, but at the moment for some reason I can't
get Flash to work in my browser, sorry.