The game is fun. I quite enjoy having to manage my ammo type and having them switch places mid games. There is potential in catching back a thrown object and using it again.
I do wish the gun felt more powerful. The slimes flying out with more velocity would be a lot more fun, especially if they can bounce around and stuff. The difficulty curve is also too loose. The game got repetitive early on although there is potential with all three slimes.
My suggestion would be to have a 'goal' wave that players are encouraged to get to and tuning the difficulty around that, with waves afterwards being implied to be very difficult.
I also think sound effects for wave completion would have added a lot more, including some kind of timer indicating the length of the wave. The balloons getting bigger is a novel concept but it doesn't let me know when they'd be set to explode. Perhaps some kind of flashing animation with an appropriate looping sound effect when it's seconds away from exploding would help.
I think a crosshair for the cursor would've also helped for this game, especially if the crosshair matches the color of the current slime.
Overall, I think the game has potential and could be polished up with fine-tuning the difficulty and having more game juice (balloons exploding animation for example) and other UX elements (The sucking effect should be feel more vibrant, perhaps maybe a screen shape along with the range being shown might help. Kirby games might be a good inspiration for how to improve it)
It's a good attempt though and it's similar to a game I've developed before for my schoolwork (A VR game where you hold two guns of different colors and have to shoot targets that match the color of the gun)