Overall, I thought this was a fun demo, with a lot of potential.
The most glaring problem with the demo is the lack of sound effects. I'm sure when those are added, it will pack a lot more punch and will be more fun to play. As it is, the lack of auditory feedback makes it seem a bit... floaty?
I found the player+enemy scaling a bit confusing, and difficult. The chests seem too random, and even with what I thought was a well-upgraded character (3 weapons, some twice, multiple level-ups and shards, 5 artifacts) I couldn't one-shot the basic slimes, and they kept multiplying. It badly affected the FPS, and by the time the potato boss came on screen no strategy was possible as there was just a swarm of slimes and constant jittering. I hope this isn't just a skill issue :D
It was unfortunate, because I couldn't experience the potato boss's unique attacks or learning timings because the game was just unplayable at that point.
So yeah, more consistent scaling and definitely adding sounds will help.
Some more minor feedback - the upgrade details red/green colouring, while "correct" (red=down, green=up) isn't that helpful at a glance to players; for example having a higher cooldown timer is bad for the player, but it's coloured green.
Green should be good, red should be bad, imo; keep it simple for the player.
Another little annoyance was with the chests. When you're in the zone and the bar starts filling up, often it's obscured by other bars and you can't see how far along it is. Sometimes the chest despawned before I could pick it up, while being in the pickup zone! I suggest once the player is in the zone, the despawn timer should deactivate.
BUG: I managed to get overlapping "Defeat" and "Level-up!" modals, which was just confusing. Defeat should clearly take priority here.
BUG: At least on the 3 browsers I tried, on itch.io, the fullscreen button make everything blank and then it was still blank when I turned off fullscreen. I had to reload the page to play again.
I had a hard time using the training ground. The GUI seemed to be cut off (and the in-game GUI was a different scale). Escape worked to close the modal, but overall I found it easier to learn by playing.
One thing I absolutely loved was the weather effects. A very neat feature there, and hopefully one which will expand in the future as different skills and different enemies behave differently in different weather.
