Nice concept! Keep it up :) I died right before killing my 3rd alien ship :O
I would have added some more variety into the game with more enemies, though for 7 days as solo it was a good way to test a single mechanic and expand, :) Well done!
One thing that I clearly see as a success, compared to mine, is that your game play loop is short enough to keep players engaged, :) Kudos! Learning by playing other people’s game is helpful :D