Fun concept, and I'm always a sucker for space stuff, and the clean vector-esque graphics are really stylish.
However there's no really obvious way to restart after you die other than reloading the page, which is annoying since the starter ship is very clunky to control. I'd suggest saving harder to control ships for later. There's also no real sense of progression other than a larger ship; even just a tracker for how many times you entered a portal would be nice.
Still overall a good game though, just needs some more polish.