As I haven't done a cleanup on a good amount of assets I'll scrap soon, the approx download size is 263 mb (but the size will still grow), and the memory use 945 mb.
(Must stress that this game is designed for offline desktop computer play)
A blank firefox with only the game running takes between 1-1,3gb of memory (sometimes 2,6gb if I start a preview while another one's in progress). Not sure if this is a result of me simply going overkill on a single level, or that I have done something wrong when assigning assets.
In Firefox the game takes roughly 30 seconds to boot up if there are no issues.