I've added music to menus and existing levels, and with that, the total game size surpassed 17 Mb of the original Goblin and Coins. My goal is still to keep it under 100 Mb if possible and so far seems very doable.
Can't say I predicted SteamDeck back in 2015 when I was working on GnC1, but I did know of 2in1 tablets using Windows and wanted people to be able to download GnC1 and play it while on commute or whatever... and those things had their storage in the form of 32-64 GB eMMC cards most of the time, as SSD's were still expensive for mainstream notebooks, with Windows itself taking a huge chunk. So 17 Mb was amazingly small and convenient download size.
It would be a bit crazy to plan for GnC2 blowing up and being super-mega-ultra-popular, of course, but that doesn't mean that some of the people playing it won't have SteamDeck or a similar device... and why not try to keep the game size down to a minimum if it can be done, for them and in general.
That way you can squeeze GnC2 in between some larger games and have it with you all the time.
Oh, also, hoping to make another playtest this winter. If you've already participated you'll automatically get access again, everyone else will be able to apply through store page during the test itself.