I think you could argue that the sword is the key item in this case haha
This is a really nice job, I like the gameplay loop and all the upgrades are pretty nice. I did end up hitting a couple bugs where the enemies stayed on screen after the wave ended/the next wave started before I finished killing everyone, then I would get immediately mobbed after buying upgrades. I think what would really elevate this would be sfx, though a week is a pretty tight crunch so I understand why you had to cut em. Maybe having the coins get pulled to you as you get closer would be nice?
Great job, this is pretty addicting!