Has potential. Pretty fun time waster for a bit, but it definitely needs more work.
After a few playthroughs I noticed that the only real challenge came from the first phase of the round, when the slimes were spawning in. They keep spawning in your path and can be hard to avoid.
But once they've finished spawning, they're no threat to you. Just run in a circle blasting fireballs until you win.
The boots were the only thing that *sometimes* seemed to help you evade spawning slimes. Which means they were the upgrade that made the biggest difference, but a lot of the time it felt luck-based.
The wand made finishing off the horde after it was done spawning less tedious, which isn't without value, but doesn't make a huge difference in game difficulty. I tried to use it to blast a path ahead of me, but the slimes are bullet-spongey and come from multiple directions so it was better not to bother.
The book was useless. It chips away at the health of the slimes chasing you, but as I explained the ones behind you are no threat. Only the ones spawning in front of you.
The laser was worse than useless. It seems designed to kill a large horde, but again the horde chasing you is no threat, only the individuals in front of you. The fact that it froze you while it was working made it dangerous to use.
More enemy variety would probably improve the strategic depth. The only VS-like game I've played is Survivor IO, and in that one, the hordes WERE a threat. You could get cornered, or caught between hordes and some enemies could outrun you, so you couldn't just run in a circle forever.
I have a suggestion for an upgrade for the future: a spyglass that let's you see more of the playfield at once. Let to have more advance warning of slimes spawning in your path.
Anyways, I clicked on newgrounds hoping for a fun distraction, and this has been it for a couple of days, so I'm happy. Keep it up!