I like chill games like this where there's just enough of a feeling of progression to keep you going! It's a difficult balance, but I think you made a smart design choice by using the upgrades to make gameplay changes visible to the player, and tying it to an in-game currency gave an added sense of reward. I definitely preferred using mouse controls because it was more responsive. I think keyboard controls could've worked if the ouroboros moved as fast that way as could be achieved with the mouse, but maybe you tried that and it was unwieldy, so I don't know. It was short and I can see how you could keep developing the concept, but it felt complete for a jam game, nice work!