@icedquinn
A long time ago, I came across a "completely legal" Microsoft Office installer, that was compressed to 100-200mb, but uncompressed to somewhere around 1200mb I think.

I only downloaded it cause I thought it was odd for it to be that small, and when I saw the compression ratio, I immediately doubted this was a proper working installer and promptly deleted it.

>i dunno how they made a pixel art adventure game that big
I imagine that when dealing to pixel art, the last thing you'll want to do is compress your images with anything that is lossy. So maybe they used a very poor lossless compression, or didn't use compression at all for the assets, so whatever compression was used for the download was massively more efficient.