First off, let me say that the web build didn't work for me (you mentioned it was buggy). However, I got the windows version to run well.
The audio and graphics of the game are pretty great. While some of the sounds, particularly on the sawblade, are a bit annoying (too much buzzing), I think the background music and the screams of the humans fit very nicely with the cartoon-y drawings. Together, they fit the theme well and give off a nice vibe.
My main concern is with different aspects of the gameplay that could be improved. I'd like it if the health bar was a bit more obvious and visible. The hitboxes seem a off, and I found it fairly difficult to actually land some of my shots, particularly on the gray humans when they were chasing me. In fact, it would be cool if hitting an enemy with the wrong type of ability had consequences. What if setting the green dudes on fire lead to less points, or if fire-ing frozen blue humans thawed them? There's a lot of potential for encouraging the player to use combos or cautious strategy in this type of game.
Building off that, why the preference for sawblade, awarding points (and the most points) for three different types of humans? More specifically, why not just spam sawblade and run around pressing spacebar as much as possible? Why not just spam all abilities while running around pressing spacebar on as many humans as possible? Again, since there don't seem to be any ways to use an ability wrong, I may as well just spam (or something similar) to achieve maximum score.
In terms of more basic things, I'd recommend adding some type of in-game tutorial and/or description of abilities; initially, I was pretty confused because I just guessed that I should use the mouse, discovered that clicking the mouse buttons did things (the game was probably reading my mouse as a controller), and kept playing with that assumption for a while. It would also be nice if the transition between timer running out and the title screen was less jarring. Maybe a scoreboard or something like that?
There are of course plenty of other things you could add or expand upon, as is the case with all games (especially those made within a 72 hour time frame). I would definitely encourage you to keep working on this title. It has a great style and I'd love to see it fleshed out more.
Congrats on the entry!