This game has potential!
I liked the idea of saving upgrades BUT it works weird, I bought melee damage and my health went down to 1, then I bought more health and got 2 health, after that I bought a laser and again I only had 1 health left. Also, at first I bought a laser and received 2 swords, but after death they disappear and even after repurchase (upgrade) they do not appear.
The game is good, but a little unclear :)