As someone with some limited web dev experience I'm impressed! It's cool that I can just expand the DOM to see the different game elements in the browser.
The gameplay loop is fun and I found myself playing it for quite a bit to see how strong I would get. There's a couple of balancing quirks though.
- The movement felt pretty clunky. I didn't really get at first what was going on and thought the portal was sucking me in, but after a while I realized that it was based on where I was aiming. Even then it felt like I was fighting the movement more than that I was controlling it. Some velocity ramping would also help.
- At first I thought I was supposed to protect the portal so I stuck around it and was confused why no enemies showed up.
- By making enemies stronger the farther away you are from the portal, it allows the player to pretty easily stack up buffs to the point where they're unkillable and only then venture out. This means that there's never any real challenge as the player can always just stick near the portal to only kill a couple enemies at a time, which is in my opinion the more optimal but boring way to play the game. Scaling the enemy spawn rate naturally over time seems like a more fun way to do it.
- The upgrades are very powerful. Especially health regen is very strong. This combined with the fact that enemies do not reapply damage if they stay in contact means that it only takes a few regen upgrades to be unkillable.
I think if you make some changes to how enemies apply damage and throw in an infinitely scaling difficulty ramp on the them with a timer on screen, this would be a super fun "survive as long as possible" type roguelike. Great job!