I really should let this whole 4k game thing go. But as I was sitting on the train today, idly hacking away at a completely different game I remembered a curious thing that I didn’t have time to investigate then. The mysterious bytes.

The compiled size of the same actionscript file will vary with up 4 bytes between compiles. You can really just bring up the command line and recompile the same file a couple of times and it will be 4098 bytes the first time and 4094 the next. Very strange. I tweeted about this suspecting some kind of metadata was stored inside the file, someone told me this shouldn’t be the case so I let it go. Turns out metadata is stored, and more than you’d think. A standard swf compiled with mxmlc can have these values:

• contributor
• creator
• date
• description
• language
• localized-description
• localized-title
• publisher
• title

The mysterious bytes come from the fact that there is a timestamp embedded, this will affect the compression of the swf making it compress a few bytes smaller if you’re lucky and a bit bigger on other occasions. These have default values, and these may be useful to keep track of stuff, they’re just a bunch of bloat to a 4k game. Luckily they’re a piece of cake to get rid off. Add these options to the compiler to set them all to be empty:

-contributor=''
-creator=''
-date=''
-description=''
-language=''
-publisher=''
-title=''

(In FlashDevelop you set these options in Project Properties -> Compiler Options -> Additional Compiler Options) However, the swf will still be up to three bytes bigger on occasion, I think the time still gets in there somehow. Nevertheless, this shaves of a whopping 40 bytes on my current version of asteroids4k!